Patent Publication Number: US-6665714-B1

Title: Method and apparatus for determining an identity of a network device

Description:
FIELD OF THE INVENTION 
     This invention relates generally to the field of information storage systems and more particularly to a method and apparatus for managing storage in a storage system. 
     DESCRIPTION OF THE RELATED ART 
     Computer systems generally include one or more host processors and a storage system for storing data accessed by the host processor. The storage system may include one or more storage devices (e.g., disk drives) to service the storage needs of the host processor. Disk drives may include one or more disks of a recording media, such as a magnetic recording medium or an optical recording medium. 
     In a typical computer system configuration, a bus provides an interconnect between the host processor and the storage system. The bus operates according to a protocol, such as the Small Component System Interconnect (SCSI) protocol, which dictates a format of packets transferred between the host processor and the storage system. As data is needed by the host processor, requests and responses are forwarded to and from the storage system over the bus. 
     With the growth of networked computer systems, multiple hosts have been coupled over a network to a shared data storage system. Fibre Channel is an example of a network that can be used to form such a configuration. Fibre Channel is a network standard that allows multiple initiators to communicate with multiple targets over the network, where the initiator and target may be any device coupled to the network. Using a network, multiple hosts are able to share access to a single storage system. One problem with coupling multiple hosts to a shared storage system is the management of data access at the storage system. Because multiple hosts have access to a common storage system, each host may physically be able to access information that may be proprietary to the other host processors. 
     Various techniques have been implemented to manage access to data at the storage system. For example, certain portions or zones of memory at the storage system may be dedicated to one or more of the hosts. Each host is ‘trusted’ to access only those portions of memory for which it has privileges. However, such an approach is vulnerable to the individual actions of each of the hosts. As a result, such a data management method may not be sufficient to protect data from unprivileged accesses. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the invention, a data management method for managing access to a storage system by at least two devices coupled to the storage system includes a step of selectively servicing, at the storage system, a request from one of the at least two devices for access to a portion of data stored at the storage system responsive to configuration data indicating that the one of at least two devices is authorized to access the portion of data. 
     According to another aspect of the invention, a computer readable medium includes a first data structure to manage accesses by a plurality of devices to volumes of data at a storage system, the first data structure comprising a plurality of records corresponding to the plurality of devices, each record of the plurality of records corresponding to one of the plurality of devices and including configuration information identifying which of the volumes of the storage system the one of the plurality of devices is authorized to access. 
     According to another aspect of the invention, a storage system includes at least one storage device apportioned into a plurality of volumes, a configuration table to store configuration data identifying which of a plurality of devices coupled to the storage system are authorized to access each of the plurality of volumes, and a filter, responsive to the configuration data, to selectively forward to the at least one storage device requests for access to the plurality of volumes received from the plurality of devices. 
     According to a further aspect of the present invention, a computer readable medium is provided. The computer readable medium is encoded with a program for execution on a computer system that includes a plurality of host processors that are coupled to a storage system over a network. The program, when executed on the computer system, performs a method including a step of displaying a first representation of each of the plurality of host processors that is logged into the storage system. 
     According to another aspect of the present invention, a method is provided for use in a computer system having a plurality of host processors that are coupled to a storage system over a network. The method includes a step of displaying, on a display in the computer system, a first representation of each of the plurality of host processors that is logged into the storage system over the network. 
     According to another aspect of the present invention, a computer readable medium is provided. The computer readable medium is encoded with a program that, when executed on a computer system including a plurality of host processors that are coupled to a storage system over a network, performs a method including steps of displaying a graphical representation of a portion of data that is stored on the storage system, displaying access privileges to the portion of data stored on the storage system, and modifying the access privileges to the portion of data by one of the plurality of host processors in response to a graphical selection of the graphical representation of the portion of data. 
     According to another aspect of the present invention, a method of managing access to data stored on a storage system from a plurality of host processors that are coupled to the storage system over a network is provided. The method includes steps of displaying a graphical representation of a portion of the data stored on the storage system, displaying access privileges to the portion of the data, and modifying the access privileges to the portion of the data by one of the plurality of host processors in response to a graphical selection of the graphical representation of the portion of the data. 
     According to a further aspect of the present invention, a computer readable medium is provided. The computer readable medium is encoded with a program that, when executed on a computer system including a plurality of host processors that are coupled to a storage system over a network, performs a method including steps of displaying a graphical representation of one of the plurality of host processors, displaying access privileges to a portion of data stored on the storage system, and modifying the access privileges to the portion of data by the one of the plurality of host processors in response to a graphical selection of the graphical representation of the one of the plurality of host processors. 
     According to another aspect of the present invention, a method of managing access to data stored on a storage system from a plurality of host processors that are coupled to the storage system over a network is provided. The method includes steps of displaying a graphical representation of one of the plurality of host processors, displaying access privileges to a portion of the data stored on the storage system, and modifying the access privileges to the portion of the data by the one of the plurality of host processors in response to a graphical selection of the graphical representation of the one of the plurality of host processors. 
     According to a still further aspect of the present invention, a computer readable medium is provided that includes a data structure to manage access by a plurality of network devices to data stored on a storage system. The data structure includes at least one record identifying each one of the plurality of network devices that is logged into the storage system. 
     According to another aspect of the present invention, a storage system is provided. The storage system includes at least one storage device, a memory that is coupled to the at least one storage device, and at least one processor that is coupled to the at least one storage device and the memory. The at least one processor stores at least one record in the memory identifying at least one of a plurality of network devices that is logged into the storage system. 
     According to a further aspect of the present invention, a method of enabling a first network device to determine an identity of the first network device is provided. The first network device is coupled to a second network device by a network. The method includes steps of sending a communication from the first network device to the second network device over the network, and requesting the second network device to identify, to the first network device, an origin from which the first communication was received. 
     According to a still further aspect of the present invention, a computer readable medium is provided. The computer readable medium is encoded with a program that, when executed on a first network device that is coupled to a second network device over a network, performs a method including steps of sending a communication from the first network device to the second network device over the network, and requesting the second network device to identify, to the first network device, an origin from which the first communication was received. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1A,  1 B and  1 C illustrate exemplary network configurations in which the data management aspect of the present invention can be employed; 
     FIG. 2 illustrates one embodiment of a packet that can be distributed between devices coupled in the networks of FIGS. 1A,  1 B or  1 C; 
     FIG. 3 is a block diagram illustrating exemplary components of a host processor and storage system which may be coupled in the networks of FIGS. 1A,  1 B or  1 C, the storage system including an adapter having elements for filtering requests issued by the host processor according to one embodiment of the present invention; 
     FIG. 4 is a block diagram of one embodiment of a configuration data structure that may be used to store filtering information for use by the storage system of FIG. 3; 
     FIG. 5 is a block diagram of one embodiment of filtering data that may be used to filter requests at the storage system of FIG. 3; 
     FIG. 6 is a block diagram illustrating exemplary components of a host processor and storage system that may be coupled in the network of FIGS. 1A,  1 B or  1 C, the storage system including logic for authenticating transactions by the host according to one embodiment of the present invention; 
     FIG. 7 is a flow diagram illustrating one method of distributing encryption keys between a host processor and storage system of FIG. 6, so that the encryption keys can be used to authenticate the identity of the host processor; 
     FIGS. 8 a-c  are a flow diagram illustrating one method of authenticating the identity of a host processor when establishing a connection between the host processor and storage system of FIG. 6 in accordance with one embodiment of the invention; 
     FIG. 9 is a diagram illustrating exemplary components that may be included in an authentication table of the storage system of FIG.  6  and that may be used to authenticate the identity of host processors according to one embodiment of the invention; 
     FIG. 10 is a flow diagram illustrating one method of performing a checksum of data transferred between an initiator and target in the networks of FIGS. 1A,  1 B and  1 C for validating data transfers in one embodiment of the invention; 
     FIG. 11 is a flow diagram illustrating one method of validating a data transfer between an initiator and target using the checksum of FIG. 10 according to one embodiment of the invention; 
     FIG. 12 is a block diagram of a storage network that includes a storage system with which various aspects of the present invention may be employed; 
     FIG. 13 is a flow diagram illustrating one method of assigning an identifier to network devices in a storage network according to one embodiment of the present invention; 
     FIG. 14 illustrates a management window for managing network devices and access to data stored on a storage system that can be provided by a graphical user interface according to one embodiment of the present invention; 
     FIG. 15 illustrates one method of graphically representing network devices and portions of data stored on a storage system that can be provided by a graphical user interface; 
     FIG. 16 illustrates one method of graphically representing how data is stored on a storage system that can be provided by a graphical user interface according to one embodiment of the present invention; 
     FIG. 17 illustrates one method of graphically representing varying levels of detail of how network devices are interconnected in a storage network that can be provided by a graphical user interface according to one embodiment of the present invention; 
     FIG. 18 illustrates a management window showing a first step in a configuration process, for configuring access to a storage system from different hosts in a storage network, using a graphical user interface according to one embodiment of the present invention; 
     FIG. 19 illustrates a management window showing a second step in the configuration process of FIG. 18, for configuring access to specific ports on a storage system, using a graphical user interface according to one embodiment of the present invention; 
     FIG. 20 illustrates a management window showing a third step in the configuration process of FIG. 18, for configuring access to a specific port on a storage system from a specific port on a host system, using a graphical user interface according to one embodiment of the present invention; 
     FIG. 21 illustrates a task list that can be displayed by a graphical user interface according to one embodiment of the present invention to confirm configuration of a specific port on a storage system from a specific port on a host system; and 
     FIG. 22 illustrates a management window showing a fourth step in the configuration process of FIG. 18, for configuring access to a specific storage volume on a storage system using a specific port of a storage system and a specific port on a host system, using a graphical user interface according to one embodiment of the present invention. 
    
    
     DESCRIPTION OF DETAILED EMBODIMENTS 
     The present invention is directed to a data management method and apparatus for managing accesses by multiple devices (e.g., host processors, file servers and the like) to data at a shared resource (e.g., a shared storage system). According to one embodiment, the shared resource selectively services requests from the devices for portions of data at the shared resource in response to configuration data associated with each of the portions of data at the resource. 
     In one embodiment, data at the shared resource is apportioned into volumes. Configuration data identifies which volumes of data are available for access by each of the devices coupled to the resource (e.g., over a network). The shared resource includes a filter that selectively forwards a request for servicing depending upon the identity of the device issuing the request and the configuration data associated with the volume to which access is sought. The filter forwards only those requests for volumes that the device has privileges to access. Requests to volumes for which the device does not have privileges are not serviced. 
     Filtering requests at the resource allows the control of the data management to be centralized in one location, rather than distributed throughout the network. Centralizing the data management control at the storage system removes the need to trust the hosts seeking access to the storage system to only access certain portions of data. 
     In one embodiment of the invention, in addition to filtering requests to support data management at the resource, security protection may be added to further secure the data at the resource. Because filtering is performed in response to the identity of the device initiating the request, data security may be compromised if a device falsely represents its identity to gain access to the resource. In addition, data transfers between the device and the resource may be corrupted by other devices coupled (e.g., over a network) to the resource. In one embodiment, an authentication method and apparatus is provided to verify that the device that is represented as the device issuing the request is truly the device that issued the request. The authentication method may therefore be implemented to overcome security problems associated with a device misrepresenting its identity to obtain data at the resource. In another embodiment, a validation method and apparatus is provided to ensure that information, transferred between the device and the shared resource is not corrupted (either inadvertently or intentionally) during transit. 
     A data management system for managing data at a resource may use any or all of these filtering, authentication and validation techniques. One exemplary system wherein the data management method and apparatus of the present invention may be employed is in a networked computer system, wherein the devices are host processors or file servers coupled to the network, and the shared resource is a storage system (e.g., a disk device storage system). It should be appreciated that the use of a network, host processor or shared disk device is not a limitation of the present invention, and that such a system configuration is described below solely for purposes of illustration. 
     In one embodiment, one or more hosts may be coupled to one or more storage systems using a network, with requests and responses being forwarded to and from the storage systems over the network according to the protocol of the network. In addition, each host and storage system may include one or more ports for interfacing the host or storage system to a corresponding one or more networks. As described above, in one embodiment, each storage system in the network includes logic for filtering received requests to manage data accesses to the storage system. 
     One exemplary network in which the present invention may be employed is a Fibre Channel network, although the present invention is not limited to the use of the Fibre Channel network or any other particular network configuration. Three example Fibre Channel network configurations are illustrated in FIGS. 1A,  1 B, and  1 C. FIG. 1A illustrates a network  10  arranged in a loop configuration, where all devices in the network are coupled together in a single loop. In FIG. 1A, three host processors  12 ,  14  and  16  are shown coupled to a storage system  20  by a hub  18   a . Internally, the hub is arranged in a loop configuration. Communication between the devices, over the busses  15   a - 15   d , is performed by passing data packets from one device to the next in the loop. FIG. 1B illustrates a network  30  arranged in a fabric configuration, where all the devices are coupled together by a switch  18   b . Communication between pairs of the devices  12 ,  14 ,  16  and  20  in the network  30  is controlled by the switch  18   b . The data management method of the present invention may be employed in networks arranged in the loop or fabric configurations illustrated in FIGS. 1A and 1B, or alternatively in other network or resource sharing configurations. For example, the data management aspect may be employed in the network illustrated in FIG.  1 C. In FIG. 1C, a host/storage system configuration is shown where the storage system includes two ports, each of which interfaces the storage system to a different network. In FIG. 1C, a first port (Port  0 ) is coupled to a fabric network  10  and a second port (Port  1 ) is coupled to a loop network  30 . 
     As mentioned above, the data management aspect of the present invention configures volumes of data at the storage system  20  according to the identity of the host devices coupled to the storage system. The configuration data that is used to manage the allocation of volumes to different hosts may be provided, for example, by a system administrator of the network. The system administrator tracks the host devices that are coupled to the network and the available volumes at the storage system. As a new host device enters the network, the system administrator allocates storage system volumes to the host. The number of volumes allocated to the host may be based on a requested number of volumes, or alternatively may be based on historical data requirements of the host. The system administrator may be implemented in software, executing on one of the devices or storage systems in the network, and may include a graphical user interface to enable users to monitor the availability and assignment of volumes to different hosts in the network. The present invention is not limited to any particular implementation of the system administrator. 
     Generally, as each device enters the network it queries the network to identify the other devices coupled to the network. Each device that responds to the query returns one or more identifiers for the device. For example, the identifier may include the world wide name (WWN) assigned to the device by the manufacturer of the adapter board using a naming convention. The identifier may also include a source identifier (ID). Both are unique identifiers for the device, however the source identifier is generally a shorter identifier than the WWN. The source identifier may identify the device (e.g., a host processor) and the port of the device that is coupled to the network. Thus, if multiple ports of the particular device are coupled to the network, an identifier may be returned for each port. When the query operation is complete, each of the devices has knowledge of the other devices coupled in the network. Once each device has knowledge of the other devices in the network, this information can be used to exchange data between devices. 
     Requests and responses to and from the storage system  20  are forwarded over the networks  10  and  30  according to the network protocol. The Fibre Channel interconnect is capable of carrying multiple interface command sets. Accordingly, the devices that are coupled together using the Fibre Channel network may communicate using any of a number of higher level protocols including Internet Protocol (IP), Small Component System Interconnect (SCSI) protocol, or any of a number of other protocols, provided that the interfacing devices have knowledge of the type of protocol that is being used on the particular Fibre Channel interconnect. Certain types of devices have historically been designed to communicate using certain protocols. For example, host processor devices have historically communicated with storage systems using the SCSI protocol. Thus, devices coupled using the Fibre Channel network may communicate with each other using the same protocols that have historically been used. As a result, existing interfaces of the devices require little redesign to couple to the Fibre Channel network. 
     Tunneling techniques typically are used to convert packets of any type of protocol into packets that may be propagated on the Fibre Channel network. Using tunneling, one packet, formatted according to a first protocol, is enveloped in a second packet formatted according to the Fibre Channel network protocol. Thus, a SCSI packet may be enveloped in a Fibre Channel packet by a host processor or storage system for transmission on a Fibre Channel network. One example of a packet formatted according to a SCSI protocol and enveloped in a Fibre Channel packet is illustrated in FIG.  2 . 
     In FIG. 2, a Fibre Channel packet  50  includes a header portion  55  and a payload portion  60 . The header portion  55  includes a source ID field  52 , a destination ID field  53  and a length field  54 . The source ID field  52  identifies a device in the network that initiated the transmission of the packet  50 . The destination ID field  53  identifies a target device for receiving the packet in the network. The length field  54  identifies a number of bytes in the packet. In addition, other fields defined in the Fibre Channel specification also may be included in the header, although these fields are omitted herein for clarity purposes. 
     The source ID field  52  and destination ID field  53  are used in the exemplary system of FIG. 1C to identify particular host processors and the storage system. When a host issues a request packet to the storage system, the source ID identifies the host and the destination ID identifies the storage system. In accordance with one embodiment of the invention, the storage system uses the source ID field  52  of the packet to index into configuration data identifying which of the volumes of data the respective host has privilege to access. 
     As mentioned above, the source ID field for a host accessing the storage system  20  can be used to identify the host that issued the request to index into configuration data for the host at the storage system. The configuration data identifies the portions of the storage system that are accessible by the host. Thus, the configuration data can be used by filter logic at the storage system to selectively service the host&#39;s request. Exemplary components of a host and storage system that may be used to implement the method an apparatus for filtering requests based on a host identifier will now be described with regard to FIGS. 3-5. 
     As described above, in one embodiment of the invention, the storage system determines whether a received request should be serviced based on the configuration data. A copy of the configuration data may be stored in a memory at the storage system. Periodically, the configuration data may be updated by the system administrator as hosts enter and exit the network. The storage system also includes logic for communicating over the network and filtering logic, coupled to the memory that stores the configuration data, for determining whether a request received from the network should be serviced. The above-described data management system may be implemented in a variety of ways and the present invention is not limited to any particular implementation. However, for purposes of clarity, one embodiment of a host processor and storage system capable of providing this data management functionality is illustrated in FIG.  3 . 
     FIG. 3 illustrates a host processor  12  coupled to a storage system  20  using a network  21 . The network  21  may be, for example, a Fibre Channel network arranged in any of the configurations illustrated in FIGS. 1A-1C. The host processor  12  may be a multi-processing unit, including one or more central processing units such as CPU  40  coupled by a local bus  43  to a memory  42 . One or more host bus adapters (FIBAs)  45  and  45   a  are coupled between the bus  43  and the network  21 . 
     Each host bus adapter (HBA)  45  and  45   a  operates to connect the host processor  12  to the network. The HBAs  45  and  45   a  translate data received from the CPU  40  into the format dictated by the protocol of the network. In addition, the HBAs  45  and  45   a  translate data received from the network in packet format into data in a format usable by the CPU  40 . 
     The host bus adapter may be implemented using a combination of hardware resident on the HBA and driver software stored in the HBA or in the memory  42 . Alternatively, the host bus adapter may be implemented either entirely in hardware or software. In one embodiment, the HBA  45  includes a processor  41  coupled to a memory  49 . The processor  41  controls the flow and format of data into and out of the HBA  45 . The memory  49  is used to provide temporary storage of data as it is transferred to and from the network. The HBA generates packets for transmission over the network  21 , with each packet including a source ID field identifying the particular HBA. Because multiple HBAs may be included at each host, multiple source IDs may be associated with the same host. It should be appreciated that the present invention is not limited to the particular implementations of host bus adapters shown in FIG. 3, as other implementations may alternatively be used. 
     The storage system  20  includes storage devices  38   a - 38   d  which may include one or more disk devices. Access to the storage devices  38   a - 38   d  is controlled through the use of disk adapters  36   a - 36   d  which may be implemented using a programmed processor or custom hardware design. In the embodiment illustrated in FIG. 3, a disk adapter is provided for each storage device  38   a - 38   d , although alternatively a disk adapter may be coupled to more than one storage device. In addition, one or more of the disk adapters  36   a - 36   d  may include secondary connections to the storage devices  38   a - 38   d  of another disk adapter  36   a - 36   d  to permit recovery from failure of one disk adapter by shifting its functions to the second disk adapter. 
     The storage devices  38   a - 38   d  are apportioned into volume sets. One or more of the volume sets may be made available to one or more of the HBAs  45 ,  45   a  or the host processor  12 . In one embodiment, references to the volumes in the storage devices  38   a - 38   d  by the HBAs are performed using logical unit numbers (LUNs). There need not be a one-to-one correspondence between the logical unit numbers provided by the host processor  12  and the physical addresses of the disk devices. 
     A configuration database  32  (FIG. 3) stores information regarding which ones of the HBAs have access to which ones of the volumes. As discussed above, in one embodiment information in the configuration database is received from the system administrator and is periodically updated as the configuration of the network changes. 
     An example of the types of data that may be stored in the configuration database  32  include a history table  69 . The history table  69  is apportioned into blocks, with one block for each of the ports of the storage system. Each block in the history table  69  includes a list of those hosts that have queried the port as they entered the network. The identification information for each host that is stored in the history table  69  may include the WWN of the host and the source ID of the host. This identification information may be used when the host logs into the storage system  20  to match an identifier of the host with configuration data for the host. The identification information that is stored in the history table  69  may also include additional information, such as an alias of the host, as described further below with respect to FIGS. 13 and 14. 
     The configuration database  32  may also include a header portion  70  for mapping the HBAs to the available ports at the storage system  20 . A volume allocation portion  72  may be provided for allocating logical volumes of data at the storage system  20  to different HBAs. A mapping portion  74  is provided for mapping LUNs to physical addresses of the disks. In addition, a filter table  76  is provided for controlling which HBAs have access to which of the LUNs. The filter table  76  is generated using the volume allocation and mapping information and includes a record for each HBA coupled to any of the ports of the storage system. An example implementation of the filter table  76  is provided in FIG.  4 . Each record  76   a - 76   n  includes the WWN associated with the HBA, a flag indicating whether the volumes allocated in this entry are shared, and a LUN map identifying which of the logical volumes the HBA may access. In one embodiment, the LUN map is in the form of a bitmask with one bit allocated to each LUN in the storage system. In one embodiment, a bit in the bitmask is set to indicate that the associated HBA indicated by the WWN has access to the corresponding LUN, although alternatively the bit may be cleared to indicate access. In addition, alternative embodiments wherein the available LUNs are indicated differently may also be used. 
     The storage system  20  (FIG. 3) also includes a filter and adapter unit  34 . The filter and adapter unit  34  translates packets received from the network into data blocks and control for forwarding to the disk adapters  36   a - 36   d . In addition, the filter and adapter unit  34  performs a filtering function to ensure that only those HBAs with privileges are able to access volumes. Thus, rather than trusting that the HBAs will only access those volumes which they have been assigned, the filter and adapter unit  34  controls accesses to the disks by filtering out non-privileged requests. 
     In one embodiment, the filter and adapter unit  34  includes a processor  80  coupled to a memory  83 . The processor is used to control the transmission and translation of data between the storage system  20  and the network  21 . The memory  83  is used to store a transient filter table  84 . The transient filter table  84  is apportioned into a number of tables, one for each port of the storage system. Each time that an HBA initiates a connection with the storage system  20  over one of its ports, filtering information is copied from the filter table  76  in the configuration database  32  to the appropriate entry in the transient filter table  84 . The filtering information may include the source ID of the HBA logged into the port, a flag indicating whether the volumes associated with this entry are shared, and a LUN map for the HBA logged into the port, where the LUN map is copied from the filter table  76  in the configuration database. 
     In one embodiment, the configuration data in the transient filter table  84  is accessed for each request. The address of the request is provided in Bus/Target/LUN format, where the Bus portion indicates the Fibre Channel network address of the storage system  20 , the Target portion indicates the storage system port address, and the LUN represents the volume address of the request. The address is compared with the entry in the transient filter table  84  which includes the LUN map associated with the HBA. If the bit in the LUN map associated with the addressed LUN indicates that the HBA has access to the LUN, the request is forwarded to the disk adapters  36   a - 36   d  for servicing. If not, the request is ignored. 
     The size of the transient filter table  84  is related to the number of ports provided at the storage system, the number of HBAs supported at each port and the number of LUNs in the storage system. An example configuration of the storage system  20  may include sixteen ports for accessing 4096 LUNs, with each port capable of supporting accesses by thirty two different HBAs. Thus, when the transient filter table  84  is large, if it was stored in a single large memory the access time for each I/O request may be long. 
     In one embodiment, to increase the response time performance of the storage system  20 , the transient filter table  84  is arranged to allow for quick retrieval of the access information for each HBA. Referring now to FIG. 5, one illustrative configuration of the transient filter table is shown. The transient filter table  84  is shown to include an array of records, such as record  400 . One column of records is provided for each LUN in the storage system (e.g., storage system  20  in FIG. 3) numbered in FIG. 5 as LUN 0  to LUNx, where x+1 is the number of LUNs in the storage system. One row of records is provided for each port at the storage system. Each record includes a bitmap  402 . The bitmap includes a number of bits corresponding to the maximum number of devices (HBAs) that can access each port. In FIG. 5, these bits are indicated as D, D 2  . . . Dn, where n is the maximum number of devices that may be coupled to any port. 
     During operation, as an I/O request is received at the storage system  20 , the address of the I/O request is compared with the data in the transient filter table  84 . The address includes an identifier of the HBA which initiated the request, and an address to the storage system portion that the host wants to access. This address includes, generally, a Bus/Target/LUN combination of fields. The bus field is the base address of the storage system  20  on the network, the target is the source ID of the port of the storage system to which the request is directed, while the LUN indicates the logical unit addressed by the request. The target information (row) and LUN information (column) are used to index into the transient filter table to obtain one of the records. The source ID for the requesting device (e.g., HBA  45  in FIG. 3) is then used to select one of the bits in the bitmap  402  of the record  400  selected by the Bus/Target/LUN address to identify whether or not the bit is set in the mapping. If the bit is set in the mapping, then the request is forwarded to the disks for servicing. If not, the request is dropped. 
     The transient filter table  84  may be stored in memory, as illustrated in FIG. 3, or may alternatively be implemented in hardware. While the configuration of the transient database described above provides one method of accessing HBA and LUN mapping information, alternative configurations may also be used. The present invention is not limited to this implementation. Rather, any configuration database arrangement that allows mapping data to be obtained from the database using a source identifier and a resource address may be used. 
     Accordingly, a data management system that reserves volumes of data for host processors based on host identifiers has been described. In one embodiment, the data management system is augmented to add security protection by authenticating each request to verify that it was truly sent by the host indicated by the host identifier received at the storage system  20 . Authentication of the connections to the storage system  20  secures the data volumes allocated to each of the host processors by verifying that the host requesting a data volume is truly the host indicated in the source ID of the request packet. Simply relying on the source identifier of the host processor may not be a sufficient measure of protection. In some insecure environments, a processor may issue a false source identifier in an attempt to access privileged data of another host. Authentication thus verifies that the host processor is who it claims to be, and therefore should be allowed access to the data. 
     In one embodiment, to support the authentication of host requests, the storage system issues a number of unique, expected identifiers to each HBA of each host device prior to the initiation of transactions by the host device. The storage system maintains a copy of the expected identifiers. When the HBA associated with the host device initiates a series of transactions, it forwards the expected identifiers that were received from the storage system back to the storage system. The storage system compares each received identifier against the expected identifier. Because the storage system only forwarded the identifiers to the particular HBA associated with the host, if the correct identifier is received, the storage system can verify that, in fact, the request was issued from the indicated host. In one embodiment, the level of security protection is further enhanced by using a random number for each identifier. In another embodiment, an encryption key, known only to the host and the storage system, is used to encrypt the identifier before it is sent to the storage system. The storage system may then decrypt the identifier using the encryption key. Encrypting the identifier prevents other devices that are coupled to the network from obtaining the identifier and gaining access to privileged data. Thus, a two-tiered level of authentication is provided, since each transaction has a unique identifier, known only to the issuing host, and the identifier is encrypted using a unique access key known only to the HBA at that host. 
     In one embodiment, the identifier information is transferred between the devices on the network (e.g., the host and the storage system  20 ) using selected fields of the packet. Referring again to the example packet of FIG. 2, illustrated in the payload portion  60  of the packet  50  are some of the fields that are used to communicate according to the SCSI protocol. These fields include a source session ID  62 , a destination session ID  64  and a data field  65 . According to the SCSI protocol, the source session ID and destination session ID are used to track an order of transactions between an initiating device and a target. The SCSI protocol allows a number of transactions to be simultaneously outstanding between an initiating device and a target device. For example, a host initiator may issue a number of I/O requests to different volumes in a target storage system. Depending upon the accessibility of each of the volumes, the order in which the responses to the requests are returned to the host may differ from the order of the issued requests. The session IDs are used to align requests with responses at the host. The session IDs provided for each transaction may be arbitrary numbers as long as they are unique across a given time period. Because the session ID may be any arbitrary number, in one embodiment the session ID fields are used to transfer unique identifier information for each transaction. 
     The above-described authentication method may be implemented in a variety of ways and the present invention is not limited to any particular implementation. However, for purposes of illustration, an embodiment of a host processor  312  and storage system  320  including components for providing the above-described authentication functionality is shown in FIG.  6 . In FIG. 6, the host bus adapter  345  stores in its memory  349  a data structure  60 . The data structure  60  includes, for each storage system  320  coupled to the HBA, a public key  61 , a private key  62 , an access key  63 , and a list  64  of one or more random numbers. Each of the keys is a field of bits which may be used to encrypt and decrypt data using techniques known to those of skill in the art. Encryption and decryption are performed by applying the bit values of the keys to bit values of data using logical operations associated with a selected encryption algorithm. The access key is a key that is dedicated to encrypting and decrypting authentication data transferred between the HBA and the associated storage system. In one embodiment, an initial value for the access key  64  is obtained using the public and private keys  62  and  63 , respectively, as will be described in more detail below. 
     To support authentication, the storage system  320  includes a filter and adapter unit  334  that may include each of the features described with regard to FIG. 3, as well as a number of other components to support authentication. The filter and adapter unit  334  includes a random number generator  82  which is used to provide random numbers used in the authentication process for each of the HBAs coupled to the storage system. Coupled to the random number generator  82  is an encrypter/decrypter  85  and a comparator  87 . The transient filter table  84 , authentication table  86 , random number generator  82 , encrypter/decrypter  85  and comparator  87  are used in conjunction to authenticate connections to the storage system  20  using a method that will be described in more detail below. 
     As described above, the authentication method involves the transfer of identifiers between the host  312  and the storage system  320  over the network  21 . In one embodiment, the identifiers are encrypted using an access key stored at the host  312  and at the storage system  320 , although this is not a requirement of the invention. FIG. 7 illustrates one method of distributing an access key to the host  312  and the storage system  320 . 
     Access keys may be provided in a number of ways, including allocating access keys to the storage system and host processors in advance of their entry to the network. Alternatively, an access key may be obtained after the host processor has entered the network in a manner described with regard to the data flow diagram of FIG.  7 . In FIG. 7, operations performed by the HBA  345  (FIG. 6) are illustrated on the left hand side of the figure, operations performed by the storage system  320  are illustrated on the right hand side of the figure, and data flows are illustrated between the two sides. At step  100 , the HBA  345  (FIG. 6) generates a public and private key pair. This can be done, for example, using known encryption software executing on the CPU  40 . The public and private key pair is dedicated to the HBA and is not accessible by any other device coupled to the network  21  (FIG.  6 ). Data which is encrypted by the public key  61  can only be decrypted using the private key  62 , while data that is encrypted by the private key  62  can only be decrypted using the public key  61 . 
     At step  102 , the HBA  345  forwards the public key  61  over to the storage system  320 . In step  101 , the storage system  320  loops, waiting for the key. When the storage system  320  receives the public key at step  101 , it proceeds to step  103 . In step  103 , using the public key  61 , the storage system  320  encrypts an access key for the HBA  345 , forwards this encrypted access key  67  back to the HBA  345  over the network  21  (FIG. 6) and terminates. Because the HBA  345  is the only device in the network that has the private key  62  that must be used to decrypt any message encrypted with the public key, other devices that are monitoring the transactions on the network will not be able to decipher the encrypted access key  67  forwarded by the storage system  320 . When it is determined at step  105  that the HBA  345  has received the encrypted access key  67 , the process running on the HBA  345  proceeds to step  106 , wherein the HBA  345  decodes the encrypted access key using the private key  62 . In addition, at step  106 , the HBA  345  stores the access key in data structure  60  with the public key  61  and private key  62  for later communications with the storage system  320 . 
     Once the host processor has received the access key, it may begin the process of issuing I/O requests to the storage system  320 . The processes by which a host processor issues an I/O request, and by which an I/O request is serviced by the storage system  320  in accordance with one embodiment of the invention will now be described with regard to the flow diagrams of FIGS. 8 a-b  and FIG.  9 . 
     In FIG. 8 a , a flow diagram is provided for illustrating one embodiment of a method that may be performed to establish a connection between the HBA  345  and the storage system  320 . In FIG. 8 a , operations performed by the HBA  345  are indicated on the right hand side of the figure, operations performed by the storage system  320  are indicated on the left hand side of the figure, and data flows are shown in between. At step  110 , the HBA  345  arbitrates for access to the storage system  320 . At step  120 , when the HBA  345  has won arbitration, it issues a control data block  112  to the storage system  320 . The control data block  112  includes the source ID of the HBA  345  and indicates that the HBA requests to be serviced by the storage system  320 . When it is determined at step  121  at the storage system  320  that there is an outstanding request from the HBA, the method proceeds to step  122  wherein in response to the host&#39;s request, the storage system  320  forwards a unique identifier  114  to the HBA  345 . In one embodiment, the identifier is a random number provided in the destination session ID  64  of the payload portion  60  of the packet  50  as illustrated in FIG.  2 . At step  122   a , after the storage system has forwarded the random number to the HBA, the storage system  320  encrypts the random number  114  using the access key and stores the encrypted random number for later comparison. 
     When it is determined at step  123  that the HBA has received the random number from the storage system  320 , at step  124  the HBA encrypts the random number  114  using the access key  63  (obtained using the process of FIG.  7 ), and returns the random number to the storage system  320  as an encrypted number  125 . When it is determined at step  126  that the storage system  320  has received a response, at step  127  the storage system  320  compares the received random number  125  against the previously encrypted and locally stored version of the random number generated at step  122 . The compare status  128  is forwarded to the HBA. If there is not a match, this indicates to the storage system that the host does not have the correct access key, and/or that the host does not know the correct random number and the connection between the host processor and the storage system is not authenticated. The HBA is not permitted to access data at the storage system  320 , and the transaction is complete. If there is a match, then the host has the correct access key, and the correct random number and connection between the HBA and the storage system is authenticated. 
     Once the connection between the HBA and the storage system has been authenticated, the HBA may send an I/O request to the storage system  320  for servicing. In one embodiment of the invention, every I/O transaction is authenticated using a different identifier (e.g. random number). Because the SCSI protocol allows for multiple I/O requests from an HBA to be outstanding at any given time, the HBA keeps track of the outstanding I/O requests using a technique referred to as command tag queuing. Each I/O request is assigned a unique tag, using the source session ID field  62  (FIG.  2 ). When a response is returned from the storage system, the tag is included in the session ID field of the response so that the response data may be aligned with the request using the tag. 
     The maximum number of I/O requests that an HBA may have outstanding at any instant in time is determined according to the command tag queuing protocol. Because each I/O request is assigned a unique identifier, each HBA should always include a sufficient number of identifiers to ensure that an identifier can be provided for each outstanding request. Therefore, according to one embodiment, as each device logs into the storage system a list of unique identifiers is forwarded to the device. The number of identifiers in the list corresponds to the maximum number of I/O requests capable of being outstanding at the device, although the present invention is not limited to this number. As each device issues a request to the storage system, one of the identifiers is used from the list. Each time that the storage system responds to a request, it returns a new identifier which is stored at the bottom of the list. Identifiers are selected in first in first out order from the list. As a result, a constant number of identifiers is maintained at the device to satisfy command tag queuing protocols. 
     One embodiment of a method of providing the identifiers to the host is described below. Because a unique identifier or random number will be associated with each I/O request, at the start of an I/O sequence, the HBA requests a number of random numbers equal to the maximum number of permissible outstanding I/O requests. The list of random numbers is stored as list  64  in data structure  60  (FIG. 6) of the HBA  345  and is additionally stored in the authentication table  86  of the filter and adapter unit  334  (FIG. 6) of the storage system  320 . 
     Referring now briefly to FIG. 9, an example of elements that may be stored in the authentication table  86  (FIG. 6) is shown. For each of the HBAs that is coupled to the storage system  320 , a data structure  89  is provided. The data structure may include a public key  89   a , which is a copy of the public key  61  that was provided by the HBA to obtain the initial access key  63 . In addition, the data structure  89  may include an access key  89   b , which is a copy of the access key  63  stored at HBA  345 . In one embodiment, each of the data structures further includes a list of random numbers. The random number in each entry of the data structure  89   c  corresponds to a random number that will be used to authenticate an associated transaction. How the random number is used to authenticate a transaction is described in more detail with regard to FIG. 8 b.    
     In FIG. 8 b , at step  184 , the HBA issues a control data block  185  to the storage system  320 . The control data block  185  includes control for notifying the storage system  320  that the HBA is going to initiate an I/O transaction, and that the connection has been authenticated. When it is determined at step  186  that a request has been received, the storage system  320  decodes the request and at step  187  forwards a packet  188  including a list of random numbers to the HBA  345 . At step  187   a , the storage system  320  also encrypts the first random number using the access key and stores the encrypted number locally for later comparison with the encrypted number received in a request from the HBA. 
     When it is determined at step  189  that the HBA has received the packet  188 , at step  190  the HBA  345  checks to determine whether there is an outstanding I/O request. If so, at step  192 , the HBA  345  encrypts the first random number using the access key, stored in field  63  of the data structure  60 . The HBA  345  then inserts the encrypted random number in the source session ID field of the I/O request packet, and forwards the I/O request packet  194  to the storage system  320 . 
     When it is determined at step  195  at the storage system  320  that an I/O request packet has been received, at step  196  the storage system  320  compares the encrypted random number received in the source session ID field of the I/O request packet  194  against the encrypted random number generated at step  187 . Alternatively, the storage system  20  may simply decrypt the received random number and compare it against the expected random number. If there is a match, the storage system  320  services the I/O request, and forwards a response packet  197  back to the HBA  345 . The response packet includes any data requested by the HBA, and a new random number which will be used once the numbers in the list  188  are exhausted. In one embodiment, the new random number is provided in the destination session ID field, while the previous, encrypted random number is returned in the source ID field for tracking purposes, although the use of specific fields is not a limitation of the present invention. 
     When it has been determined at step  198  that a response has been received from the storage system  320 , the HBA retrieves the non-encrypted random number from the session ID fields of the packet  197  and stores the random number in the data structure  60 . The process then proceeds to step  190 , where the HBA initiates the next I/O request, using the next random number from the random number list  64  encrypted using the access key. 
     Thus, a method is provided wherein unique identifiers are used to authenticate a host at a storage system. Although the method has been described using random numbers, it should be understood that this is not a requirement of the invention, and that any sequence of numbers that does not include a readily discernable pattern may alternatively be used. As discussed above, more than one HBA may be simultaneously connected to the storage system  320 . Thus, as identifiers are distributed to coupled HBAs, their sequence will similarly be distributed among the variety of HBAs that are coupled to the storage system  320 , thereby making the number distribution appear even more random and accordingly more secure. In addition, although encryption techniques have been described, it is not a requirement of the invention that identifiers be encrypted prior to transfer. Alternatively, an authentication technique may be used which does not include identifiers for each request but encrypts the entire request using the access key. It is also envisioned that a different access key may be provided for each transaction. The present invention may incorporate any combination of these authentication techniques and is therefore not limited to the specific embodiments discussed above. 
     The above techniques may be used to verify that a connection between an initiator and a target is authorized. In another embodiment, techniques are also used to ensure that the data that is received at the target is the data that was sent by the initiator. Accordingly, further security may be obtained by applying validation methods to ensure that commands and data are not corrupted during a transfer from the initiator to the target. The validation method may be provided to preclude other devices that are coupled to the network from interfering with transactions between the initiator and the target. 
     According to another aspect of the invention, a method for validating a data transfer between a source and a target over the network includes the step of maintaining, at both the target and the initiator, a digital signature of the transfer. The digital signature is in the form of a checksum. Each byte of data that is transferred between a target and an initiator is combined with the previous bytes of the transfer using a hashing function to form the checksum. The hashing function may be, for example, an exclusive OR function, or some derivative thereof. The data included in the signature may include only that data forwarded by the initiator to the target, only that data forwarded from the target to the initiator, or a combination thereof. 
     Referring now to FIG. 10, a flow diagram of one embodiment of a method for validating a data transfer between an initiator and a target is shown. The flow diagram is similar to that described with regard to FIG. 8 b , but includes steps for validating the data transfer. At step  200 , it is determined at the initiator whether or not there are any I/O requests. If so, at step  202 , the initiator encrypts the random number associated with the transaction and forwards the I/O request, with the encrypted random number in the source session ID, to the target. When it is determined at step  204  that the target received the request, at step  205  the target compares the received encrypted number against a stored encrypted expected random to determine a match. If there is no match, the target does not respond. If there is a match, at step  206  the target forwards a new encrypted random number and response data to the target. Also, at step  206 , the target hashes the response data into the existing checksum to provide a new checksum to build the digital signature of the data transfer. The response  207  is received at the initiator in step  208 . At step  209 , the initiator also hashes the response data into the existing checksum to provide a new checksum to build the digital signature of the data transfer. The process of issuing I/O requests and generating checksums continues for the number of requests in the initiator/target connection. When it is determined at step  200  that there are no more requests, the process proceeds to the validation phase in step  210 , illustrated in FIG.  11 . 
     At step  210 , the initiator encrypts the checksum using the access key, and forwards the encrypted checksum  212  to the target. The target receives the encrypted checksum, at step  214 . At step  216 , the target decrypts the checksum and at step  218  the target compares the decrypted checksum with the checksum generated by the target. The target sends a status packet  220  to the initiator indicating whether or not the checksums matched. If it is determined at step  222  at the transaction was valid (i.e, no data was corrupted), then the connection between the initiator and the target is completed. If the status  220  indicates that the transaction was not valid and that data was corrupted, then the initiator re-establishes the connection with the target and repeats the data transaction. 
     Thus, a data management method and apparatus has been described that provides three levels of data management. Filtering is provided to ensure that each host only accesses volumes of data for which it has privileges. Security may be incorporated using authentication methods to verify that each request was truly issued by the host indicated in the identifier of the request. Finally, validation may be provided to ensure that data is not corrupted during transit. A system using the data management method and apparatus of the present invention may incorporate one or more of these levels of data management independently, and thus the present invention is not limited to a system including all the recited data management techniques described above. Such a data management system provides increased control over data accesses by users at a host processor by limiting the data capable of being accessed by the host processor. Thus, while users at a host processor may be capable of accessing all of the data allocated to the host processor (depending upon the privileges associated with the user), no user, not even a system administrator with the highest privilege at the host processor, is capable of accessing data that is not allocated to the host by the storage system, regardless of the privileges of the user on the host. 
     Although the above discussion relates to an exemplary system wherein a host gains access to data at a storage system, the above described methods may be applied to any system wherein a resource is shared by multiple devices. Such systems include, but are not limited to any type of storage system including disk devices, tape devices, file servers and the like. 
     According to a further aspect of the present invention, a user interface for a system administrator is now described. The user interface communicates with a configuration database (e.g., configuration database  32  in FIG. 3) of a storage system to enable a user or another application program to view and manage the availability and assignment of data storage volumes to different hosts in a storage network. As used herein, the term “storage network” is used to describe any type of network in which at least one host (e.g., host processor  12  in FIG. 3) is coupled to at least one storage system (e.g., storage system  20  in FIG. 3) using a network connection that permits additional network devices (such as hosts, HBAs, storage systems, switches or hubs, etc) to be interconnected therewith. Advantageously, the user interface permits network devices to be viewed and managed using identifiers that are more meaningful to a user than a WWN. 
     In one embodiment of the present invention, a graphical user interface (GUI) is provided with which a user can graphically view the availability and assignment of data storage volumes to different hosts in a storage network. The GUI also allows a user to graphically view the topology of the network (i.e., how network devices such as hosts, HBAs, storage systems, storage system adapters, etc., are interconnected in the network), and to graphically modify the topology of the network and/or the availability and assignment of storage volumes to different hosts in the network. Advantageously, the GUI permits network devices and the availability and assignment of storage volumes on a storage system to be viewed, managed, and modified using an alias for each host/HBA pair that is more meaningful to a user than a WWN. 
     In another embodiment of the present invention, a command line interface (CLI) is provided that can be used to query the availability and assignment of data storage volumes to different hosts in the network. The command line interface allows a user or another application program to generate reports illustrating the topology of a storage network (i.e., how network devices such as hosts, HBAs, storage systems, storage system adapters, etc. are interconnected in the network), and to modify the topology of the network and/or the availability and assignment of storage volumes to different hosts in the network. Advantageously, the CLI permits network devices and the availability and assignment of storage volumes on a storage system to be viewed, managed, and modified using the WWN of the device, or a more meaningful identifier that can be assigned by a user or by the storage system. 
     Embodiments of a user interface may advantageously be implemented in software that executes on a central processing unit of a host, such as CPU  40  of host processor  12  (FIG.  3 ). During execution on the CPU of a host processor, the user interface is typically stored in the memory (e.g., memory  42 ) of the host processor, although the interface software may be stored on any computer readable medium, such as diskette, tape, CD-ROM, etc., that is accessible by the host processor. In one embodiment of the present invention, a Java-based graphical user interface is provided. In another embodiment, a C-programming language based command line interface (CLI) is provided. However, it should be appreciated that the present invention is not limited to any particular software implementation, as any of a variety of implementations may be used. 
     Embodiments of a user interface according to the present invention may advantageously be implemented on a single host, or on a number of hosts distributed throughout a storage network. Moreover, embodiments of the user interface may be used to view and manage the availability and assignment of storage volumes on a single storage system or on multiple storage systems. Because the user interface may be used to modify the connection and allocation of storage volumes to different host/HBA pairs, the user interface may include password protection so that only authorized personnel can access the interface. Alternatively, for security reasons, the ability to modify the connection and allocation of storage volumes to different hosts on the storage network may be limited to a particular host. As used herein, the term “administrator host” is used to refer to any host on which the user interface is implemented and from which the availability and assignment of data storage volumes to different hosts can be modified. In one embodiment, portions of the user interface may be installed on other hosts so that they may be able to view the storage topology of the network, without having the ability to modify connections and allocation of storage thereto. 
     Each of the above-described embodiments of a user interface access a configuration database (e.g., configuration database  32 , in FIG. 3) that is stored and maintained on a storage system to manage access within a storage network. According to a further aspect of the present invention, the configuration database  32  may include additional identification information, in addition to the WWN and/or source ID of the host/HBA, to facilitate the management of access in the storage network. In one embodiment, the configuration database may include an alias for each host, HBA, and filter and adapter unit known to the storage system, as well as an alias for the storage system itself. Thus, when managing access to storage volumes in the storage system, a user need not know in advance which WWN is associated with a particular network device to manage that device. 
     FIG. 12 illustrates an exemplary storage network  1200  that will be used to describe various aspects of the present invention. It should be appreciated that the network topology illustrated in FIG. 12 is exemplary only, as embodiments of the present invention can be used with network topologies that are different (e.g., more complex, or less complex) than that shown in FIG.  12 . 
     As shown in FIG. 12, a number of host processors  1212 ,  1214  are coupled to a storage system  1220  using a network  1221 . Host processor  1212  has been assigned Internet Protocol (IP) node name “lo 10239 ”. As known to those skilled in the art, an IP node name is an alphanumeric identifier for a network device that corresponds to a unique IP address that the network device uses to communicate with other network devices on an IP network. Host processor  1212  includes two HBAs, HBA  1245   a  and HBA  1245   b . Host processor  1214  has been assigned IP node name “cohen 4554   b ” and includes a single HBA, HBA  1245   c . For the purposes of illustration, host processor cohen 4554   b  is designated as the control station or administrator host, from which connection and access to storage is controlled. 
     Storage system  1220  is similar to the storage system  20  described above with respect to FIG.  3 . However, in contrast to the storage system  20  of FIG. 3, storage system  1220  includes a plurality of filter and adapter units  1234   a ,  1234   b , and  1234   c , such as would typically be used in a larger network where many different hosts share the use of a central storage system  1220 . One such storage system that is representative of storage system  1220  is the Symmetrix line of disk arrays available from EMC Corporation of Hopkinton, Mass. The Symmetrix line of disk arrays is described in numerous publications from EMC Corporation, including the Symmetrix Model 55XX product manual, P-N200-810-550, rev. F, February, 1996. 
     As shown in FIG. 12, each filter and adapter unit  1234   a ,  1234   b , and  1234   c  has its own connection to the network  1221 . Each filter and adapter unit may include a number of ports, with each port supporting one or more connections to a host processor/HBA. For example, each filter and adapter unit may include two ports, with each port being capable of supporting up to 32 different connections to a host processor/HBA. Each of the filter and adapter units communicates with the configuration database  1232  that is maintained by the storage system  1220 , and may include a processor and a memory, such as processor  80  and memory  83  described with respect to FIG.  3 . Multiple filter and adapter units, such as shown in FIG. 12, may be used to connect to different types of networks (e.g., a loop network or a fabric network), for fault tolerance reasons, to increase bandwidth, or for a variety of other reasons. 
     According to a further aspect of the present invention, configuration database  1232  may include other information pertaining to network devices in the storage network in addition to that described above with respect to configuration database  32  in FIG.  3 . This additional information can include, for example, the IP node name of each host that is logged into the storage system  1220 , the IP node name of each host that has been assigned storage volumes in the storage system, or both. According to one embodiment of the present invention, additional information pertaining to devices in the storage network is stored in two different portions of the configuration database  1232 ; i.e., the history table  1269  and the configuration portion  1275  of the configuration database  1232 , including header portion  1270 , volume allocation portion  1272 , mapping portion  1274 , and filter table  1276 . The additional information that is stored in the history table  1269  is maintained on a temporary basis for each host/HBA pair that is logged into a port of the storage system. In contrast, the additional information that is stored in the configuration portion  1275  is maintained on a permanent basis for each host/HBA pair for which access to storage volumes has been defined. It should be appreciated that the additional information pertaining to devices in the storage network need not be stored in different portions of the configuration database  1232 , as the present invention is not so limited. 
     The additional information that is maintained in the history table  1269  can include, for each host/HBA pair that is logged into a port on the storage system  1220 : the IP address of the host, the IP node name of the host, a time stamp indicative of the time at which the host/HBA pair logged into the port of the storage system, the type of file system used by the host, and an alias for the host/HBA pair that is logged into the particular port. Moreover, the additional information that is maintained in the history table  1269  can vary depending upon the type of network device (e.g., a host/HBA pair, a switch or hub, etc). In one embodiment of the present invention, a unique alias can be automatically provided by the storage system for each host/HBA pair when the host/HBA pair logs into a port of the storage system. The unique alias includes the IP node name of the host and the name of the adapter that logged into the port. This alias, called an ASCII World Wide Name (AWWN) herein, provides a short-hand identifier for each host/HBA that is logged into a port of the storage system, and is more meaningful to a user than a WWN. This is because the AWWN is logically related to identifiers (the IP node name of the host and the name of the adapter) that are used for other purposes, such as sending electronic mail, initializing devices in a startup file, etc. 
     Advantageously, as described further below, the AWWN that is maintained in the history table  1269  can be used to view and manage network devices on a storage network and to control the availability and access to storage volumes on the storage system using embodiments of the user interface. Thus, a user can view and manage network devices using an alias that is logically more descriptive than a WWN. Moreover, a user can assign a different alias to each host/HBA pair, should this be desired. 
     The additional information that is stored in the configuration portion  1275  of the configuration database  1232  (as compared to database  32  in FIG. 3.) can be the same or similar to the additional information provided in the history table  1269 , such as the IP node name of a host, the IP address of the host, and an alias of each host/HBA pair for which access to storage volumes has been previously defined. In contrast to the information stored in the history table  1269 , the information stored in the configuration portion  1275  of the configuration database  1232  is maintained for each host/HBA pair for which access to storage volumes has been defined. According to one embodiment of the present invention, when a host/HBA pair, or other type of network device, logs into a port on the storage system, the configuration portion  1275  of the configuration database  1232  is scanned to determine if an alias for this host/HBA pair (or other type of network device) has been previously defined. When it is determined that an alias for a particular host/HBA pair (or other type of network device) has been previously defined in the configuration portion  1275 , that alias is automatically written into the history table  1269  along with its WWN and source ID. 
     According to a further embodiment of the present invention, the information that is stored in the configuration database  1232  may be stored in different areas of the storage system  1220 . In one exemplary implementation, the information stored in header portion  1270 , volume allocation portion  1272 , and mapping portion  1274  of the configuration database  1232  is stored in one or more of the storage devices  1238   a - 1238  of the storage system  1220 , while the information stored in the history table  1269  and filter table portion  1276  is stored in a different type of memory device. For example, the information stored in the history table  1269  can be stored in a centrally accessible RAM or cache memory (not shown) of the storage system  1220 , while the information stored in the filter table  1276  can be stored in a transient filter table in a memory of a filter and adapter unit (e.g., transient filter table  84  in memory  83  of filter and adapter unit  34  in FIG.  3 ). The above described use of separate storage areas for different portions of the configuration database  1232  optimizes the use of memory resources in the storage system  1220 . Specifically, rather than storing the entire configuration database  1232  in a faster access (but expensive) RAM or cache, or in a slower access (but relatively inexpensive) storage device, those portions of the configuration database  1232  that are more frequently accessed and/or temporary (e.g., history portion  1269 ) can be stored in RAM or cache, while those portions of the configuration database  1232  that are less frequently accessed and/or persistent (e.g., volume allocation portion  1270 ) can be stored on disk or other type of storage device. Although the above described apportionment of the configuration database  1232  can be used to achieve a more optimal utilization of memory resources, it should be appreciated that the present invention is not limited to a particular manner in which the configuration database  1232  is apportioned, or to a particular type of memory device in which portions of the configuration database  1232  are stored, as other implementations may alternatively be used. 
     According to another embodiment of the present invention, a utility is provided for providing additional identification information pertaining to hosts and host/HBA pairs that are logged into a storage system. The utility may be used to provide an alias for a host/HBA pair in the history table  1269  when one has not been previously defined in the configuration portion  1275  of the configuration database  1232 . The alias can then be used to view and manage that host/HBA pair and to configure storage volume assignments therefor. The utility may be implemented in software that executes on the CPU of a host processor to include this additional information in the history table  1269  of the configuration database. A flow diagram illustrating one implementation of the steps that may be performed by this utility is now described with respect to FIG.  13 . 
     At step  1310 , the utility queries the host processor to determine information such as the IP node name of the host and the IP address of the host. Other information may also be obtained, such as the manufacturer of the host processor, the type of operating system (e.g., Unix, Windows NT, Sun SOLARIS) being used on the host, etc. After obtaining information relating to the host, the utility proceeds to step  1320 . At step  1320 , the utility queries the storage network to identify those storage systems connected to the storage network that include a configuration database that facilitates shared access to storage resources, such as configuration database  1232  (FIG.  12 ). In a fabric storage network topology, this may be performed by accessing a nameserver on the fabric and examining the WWNs of devices that are connected thereto. For example, because each WWN includes a portion that is unique to each device manufacturer, the utility can examine the list of WWNs to identify those storage systems that are made by a particular manufacturer that include a configuration database  1232 . In a loop storage network topology, similar information may be obtained by querying each device in the loop and examining the WWNs of each device in a similar manner. Upon identifying those WWNs that identify storage systems that include a configuration database  1232 , the utility performs steps  1330  through  1380  for each such storage system. 
     At step  1330 , the utility logs into a port on a storage system having a configuration database  1232  and proceeds to step  1340 . At step  1340 , the utility examines the history table  1269  in the configuration database  1232  to determine if an alias already exists for the particular host/HBA pair that the utility has caused to log into the storage system. When it is determined that the history table  1269  already includes an alias for this particular host/HBA pair, the. utility proceeds to step  1380 , described further below. Alternatively, when it is determined that the history table  1269 . does not include an alias for this particular host/HBA pair, the utility proceeds to step  1350 . 
     At step  1350 , the utility examines the configuration portion  1275  of the configuration database  1232  to determine if an alias has been defined therein for this particular host/HBA pair. When it is determined that an alias has already been defined for this particular host/HBA pair in the configuration portion  1275  of the configuration database  1232 , the utility proceeds to step  1360 , wherein the alias defined in the configuration portion  1275  is written into the history table  1269 . Alternatively, when it is determined that an alias has not been defined in the configuration portion  1275  of the configuration database  1232  for this particular host/HBA pair, the utility proceeds to step  1370 . 
     At step  1370 , the utility creates an alias for the host/HBA pair that is currently logged in to the storage system and writes it into the history table  1269 . In one embodiment of the present invention, the alias includes the IP host name of the host and the name of the adapter that logged into the port. This alias, called an ASCII World Wide Name (AWWN), provides a short-hand identifier for the host/HBA pair that has more meaning to a user than a WWN. According to one aspect of the present invention, the portion of the AWWN representing the adapter name varies dependent upon the type of host (e.g, Windows NT, Sun SOLARIS, HP-UX, etc.) that logged into the port. For example, on a Windows NT host, the adapter portion of the AWWN is expressed in the form “adapterN”, where “N” is the logical number of the HBA adapter on the host. On a Sun SOLARIS host system, the adapter portion of the AWWN is expressed in the form “sbus, fca@adapter”, where “sbus” is the number of the bus on which the HBA resides, and “adapter” is the logical number of the adapter on the host. 
     After any of steps  1340 ,  1360 , or  1370 , the utility proceeds to step  1380 . At step  1380  the utility returns to the host processor the information that is now stored in the history table  1269  of the configuration database  1232 . This information will include the AWWN of the host/HBA pair, as well as any AWWNs of other host/HBA pairs that are present in the history table  1269  (e.g., AWWNs that have been previously assigned through the use of the utility on a different host processor, etc.). The utility also provides the host processor with the WWN of the host/HBA pair that logged into the storage system, a port identifier of the port on which the host/HBA pair logged into the storage system, and the device name or path (in terms of the host system) by which the storage system was reached. After providing this information, the utility then terminates. It should be appreciated that in a storage network that includes more than one storage system having a configuration database  1232 , the utility will provide this information for each storage system that it is permitted to log into. 
     As should be appreciated from the foregoing description, the above utility is capable of identifying each host/HBA pair that is presently logged into the storage system in terms of its WWN. In addition, where a host/HBA pair that is logged into the storage system has been given an alias or AWWN, the AWWN of each host/HBA pair is also provided. As described further below, this information provided by the utility can then be used by the host on which the utility was executed to view and manage network devices on a storage network and to control the availability and access to storage volumes on the storage system with a user interface. Advantageously, by executing the utility on the same host that executes the user interface, a user can view and manage network devices with the user interface using the AWWN, rather than the more arcane and cumbersome WWN. In addition, by executing the utility on a host processor, the utility can be used to identify the WWN of the HBA that the utility used to access the storage system. It should be appreciated that this ability to identify the WWN of an HBA that is connected to a network is of great use. Although the WWN of an HBA is typically indicated on the HBA itself, it may be difficult to view this information once the HBA is installed in a host processor. Moreover, although the WWN of an HBA may be identified in documentation that accompanied the HBA, such documentation is frequently lost or misplaced. Advantageously, the above-described utility allows the WWN of a network device (e.g. a host/HBA pair) to be determined by requesting another network device (e.g., storage system  1220 ) to identify the WWN of the network device with which it is communicating. 
     According to another embodiment of the present invention, a user interface is now described, that, when executed on a processor (e.g., the CPU of a host processor), enables a user to view and manage devices in a storage network. One exemplary implementation of a user interface that may advantageously be used with a storage system  1220  such as shown in FIG. 12, is described in a publication entitled, EMC Volume Logix Product Guide, Version 2.0, p/n 300-999-024, available from EMC Corporation, and incorporated by reference herein. The Volume Logix product Guide describes an implementation of a system administrator, called “Volume Logix”, that includes a software based user interface that can be used on a wide variety of different host computer platforms, including personal computers, workstations, and mainframe computers running a wide variety of operating systems, such as Windows, Windows 95 or Windows NT, Unix, Unix-variants, etc. 
     According to one embodiment of the present invention, the user interface executes on a host processor and allows a user or another application program to query a storage system and define access control for storage volumes on that storage system for network devices on a storage network to which the storage system is attached. Using the user interface, one can identify various devices (storage systems, storage system port adapters, hosts, HBAs, etc.) in the storage network and understand the relationship of these devices to one another in the storage network. For example, one can view which host processors can communicate with a storage system, the path or physical connection by which they communicate, which storage volumes of data are accessible to a particular host processor or are shared among a number of host processors, etc. In addition, the user interface can be used to modify the configuration of devices in the network, as well as manage access to storage volumes. This may be done in two different ways. In one embodiment, a graphical user interface (GUI) based software application is provided that allows one to view and modify relationships among network devices graphically. In another embodiment, a command line interface (CLI) is provided that permits one to perform similar functions as the GUI. Using either one of these interfaces, one can display listings of devices, modify relationships of devices (e.g., assign, revoke, modify privileges on storage volumes for hosts that are connected to the network), etc. Furthermore, with each of these interface, one can also modify properties that are associated with network devices. For example, one may modify the host name or the AWWN that is associated with a particular device. 
     The Volume Logix Product Guide also describes one exemplary implementation of a utility, called VCMFIND, that is similar in functionality to the utility described with respect to FIG.  13 . In accordance with one aspect of the present invention, the VCMFIND utility can be used to identify, by WWN, each host/HBA pair that is logged into a storage system, to assign an alias or AWWN by which a host/HBA pair may be viewed and managed, and to provide a copy of the contents of the history table showing all other host/HBA pairs logged into a storage system to a host processor. This information returned to the host processor by the VCMFIND utility can be used in conjunction with embodiments of the user interface to permit the management of network devices through the use of the more meaningful alias or AWWN, rather than by use of the WWN. 
     FIG. 14 illustrates one exemplary implementation of a top-level display screen that can be provided by a graphical user interface (GUI) according to one embodiment of the present invention. When executed on a host processor, the GUI provides a management window  1400  to enable a user to view, configure, or modify the manner in which devices are connected to one another, and to view, configure, or modify the allocation and access to storage volumes on a storage system. The GUI may be executed on a host processor after a utility, such as that described above with respect to FIG. 13, was executed on each host processor (e.g., host processor cohen 455   b  and host processor lo 10239 , in FIG. 12) for which management was desired. As noted above, the execution of the utility of FIG. 13 permits devices to be managed by an alias that is more meaningful than a WWN. 
     The top level GUI management window  1400  can include a number of components, such as a storage network topology pane  1410 , a storage system volumes view pane  1420 , a menu bar  1430 , a tool bar  1440 , and a status bar  1450 . It should be appreciated that the present invention is not limited to the particular arrangement of components shown in FIG. 14, as the GUI management window  1400  can be organized in many different ways. The storage network topology plane  1410  can be used for viewing network devices and the topology of the storage network at varying levels of granularity. The volumes view pane  1420  can be used to identify volumes of data stored on a particular storage system, to identify types of storage volumes stored on a particular storage system, whether those storage volumes are accessible by more that one host processor, etc. The menu bar  1430  provides a set of pull down menus,  1460 - 1480 , that allow a user to manage and control devices connected to the storage network, including controlling which host processors can access storage volumes on the storage system. The tool bar  1440  provides a quick access to some of the more frequently used options provided by the menu bar  1430 . The status bar  1450  provides informational messages relating to current actions selected from the menu bar and the tool bar, such as whether tasks are pending, whether a task has been completed, etc. 
     The GUI management window  1400  displays devices, such as host processors, storage systems, host bus adapters, storage system adapters, etc, in a storage area network, with each device being represented by an easily recognizable icon. The GUI management window  1400  also displays different types of storage volumes within a storage system by an easily recognizable icon. One exemplary illustration of how different types of storage area network devices and different types of storage volumes may be represented is shown in FIG.  15 . It should be appreciated that the present invention is not limited to any particular form of icon, as others may alternatively be used. 
     Storage system icon  1505  represents a storage system that is available on the storage network. The storage system icon  1505  may be displayed in either a collapsed form or an expanded form, as described in more detail further below. Storage port icon  1510  represents an adapter port (e.g., filter and adapter unit  1234   a-c  in FIG. 12) on a storage system. Where the storage port represented by the storage port icon  1505  is adapted for use in a Fibre Channel environment, the storage port icon  1505  may be designated an FA (Fiber channel Adapter) port (See FIG.  14 ). It should be appreciated that other types. of storage port adapters, other than a Fibre Channel adapter, may be represented, using different icons, or the same icon, but with a different textual label adjacent thereto. 
     Host processor icon  1515  represents a host processor that is available on the storage area network. The host processor icon  1515  may also be displayed in either a collapsed form or an expanded form, as described in more detail further below. Administrator host icon  1520  represents an administrator host processor or control station that is available on the storage area network and from which network devices and the allocation of storage devices in a storage system can be controlled or configured. The administrator host permits the allocation of volumes and the modification of how devices are connected in the storage network to be managed from a central control station or host processor. Like host processor icon  1515 , the administrator host icon  1520  may be displayed in either a collapsed form or an expanded form. Host Bus Adapter (HBA) icon  1525  represents an HBA by which a host processor is connected to the storage area network. The HBA icon  1525  is displayed when the host processor icon  1515  or the administrator host icon  1520  is displayed in an expanded form. 
     Storage volume icon  1530  represents a storage volume in a storage system. More specifically, storage icon  1530  indicates that the represented volume is a standard fixed block addressing (FBA) volume that has not been allocated to a particular host processor/HBA pair (i.e., a storage volume for which no assignment has been defined in the configuration database  1232  (FIG.  12 ). Assigned storage volume icon  1535  represents a storage volume in a storage system that has been assigned to a particular host processor/HBA pair in the configuration database (i.e., configuration database  1232 , in FIG. 12) of the storage system. Shared, assigned, storage volume icon  1540  represents a storage volume in a storage system that has been assigned to more than one host processor/HBA pair in the configuration database  1232  of the storage system. Configuration database storage volume icon  1545  represents that the particular storage volume stores the configuration database (called a Volume Configuration Management database, or VCM in one implementation). Mirrored storage volume icon  1550  represents that the particular storage volume functions as a mirror to another storage volume (called a Business Continuity Volume, or BCV in one implementation). Concatenated storage volume icon  1555  represents that the particular volume is one of a concatenated group of adjacent storage volumes that appear as one target volume (called a Meta Volume in one implementation). Other icons may be provided for other storage system resources. As should be appreciated by those skilled in the art, the use of different icons to represent various types of network devices and various types of storage volumes allows a detailed description of a storage network to be effectively communicated to a user. 
     Referring back to FIG. 14, the storage network topology pane  1410  provides a graphical representation of how network devices are arranged in a storage area network. This graphical representation uniquely identifies each network device in the storage area network and shows the path by which the network devices are interconnected. As described further below, this graphical representation of network devices can be displayed at varying levels of detail, selectable by a user. 
     As shown in FIG. 14, the storage network topology pane  1410  shows paths between different host processor/HBA pairs and storage system/port pairs in the storage network that may be configured or modified using the graphical user interface. Dashed grey lines are used to represent paths that connect various devices in the storage network. Black solid lines are used to represent a path between network devices in which one of the network devices has been selected, for example, by using a mouse. In the example of FIG. 14, host processor lo 10239  has been selected in an expanded form, and thus, the path between this host processor, and its two HBAs (“1f, 0,fca@3,0,” and “1f,0,fca@1,0”) are shown in solid line form. As noted above with respect to FIG. 13, the particular alias that is used to represent the HBA can indicate the type of host processor to which the adapter is attached. Other ways of representing the above information may alternatively be used, as the present invention is not limited to a particular manner of representation. Moreover, it should be appreciated that other network devices, such as switches and hubs, that are not under the control of the graphical user interface, may also be depicted in the view presented by the storage network topology pane  1410 . 
     Host processor/HBA pairs are shown on the left hand side of the storage network topology pane  1410 , with storage systems shown on the right. For example, in FIG. 14, two host processors cohen 4554   b  and lo 10239  are shown in the left hand side of the storage network topology pane  1410 , with a storage system  01836000314  shown on the right. Each type of device (network device or a device within storage system) is represented by an icon that identifies the type of network device or the type of storage volume, as described above with respect to FIG.  15 . Furthermore, each icon includes some associated text that uniquely identifies the particular device that the icon represents within the storage area network. The text that is associated with each host processor icon and HBA icon is based on the alias information of the history table  1269  (FIG.  12 ). 
     As may be seen from FIG. 14, the host processor icons of host processor cohen 4554   b and host processor lo 10239  are similar, but different. Specifically, the host processor icon of host processor cohen 4554   b  includes an “A”  1485  indicating that the host processor cohen 4554   b  has been designated as the “administrator host” or control station on which the GUI is executed, and from which network devices and the allocation of storage devices can be centrally controlled or configured. 
     As noted above, the icons for host processors and for storage systems can be displayed in either a collapsed form or an expanded form that is selectable by the user. A collapsed host icon hides the HBAs attached thereto, whereas an expanded host icon shows each of the HBAs that are attached to the host processor. Each of the host processor icons depicted in FIG. 14 is displayed in its expanded form, showing its attachment to a particular HBA on a respective host processor. When depicted in an expanded form, the host processor icon includes a minus sign  1490  indicating that the collapsed form of the host processor icon may be selected by clicking on this region (termed a “hot spot”) of the icon. Alternatively, the collapsed form may be selected by using a button associated with the tool bar  1440 , or by accessing a menu within the menu bar  1430 . When a host processor icon is collapsed, path connections between the host processor and other devices in the storage network are drawn directly from the host processor to the storage system or storage system port, depending on whether the storage system is shown in its collapsed or expanded form. When depicted in a collapsed form, the host processor icon includes a plus sign ( 1715  in FIG. 17) indicating that the expanded form of the host processor icon may alternatively be selected. An example of a host processor displayed in a collapsed form is shown in FIG. 17, described further below. 
     As noted above, storage systems are shown on the right hand side of the storage network topology pane  1410 . Storage system icons can also be shown in either a collapsed form or an expanded form. A collapsed storage system hides the ports residing on it, while an expanded storage system shows each port residing on the storage system. When a storage system is collapsed, path connections are drawn directly from the storage system to the host or HBA. When the storage system is expanded, path connections are drawn from the storage system to the port and then to the host for HBA. In FIG. 14, storage system  0183600314  is shown in an expanded form. In a manner analogous to the host processor icon, a collapsed storage system icon can include a plus sign indicating that the expanded form of the storage system icon may alternatively be displayed upon selection, and an expanded storage system icon can include a minus sign indicating the collapsed form of the storage system icon may alternatively be displayed upon selection. 
     Each host bus adapter icon (e.g., adapter 0 ) represents a particular HBA on which a host processor communicates to the storage network. Each HBA is identified using an icon and the adapter portion of the ASCII readable WWN (AWWN) that is stored in the history table  1269  of the configuration database  1232  (FIG.  12 ). As noted above, the AWWN can be assigned using a utility such as that described with respect to FIG. 13, or can be assigned automatically when a host/HBA pair logs into the storage system and the AWWN has been previously defined in the configuration portion  1275  of the configuration database  1232 . Moreover, a user can change the AWWN that is assigned to a particular host/HBA pair in the configuration portion  1275  of the configuration database  1232  using the GUI. The naming convention used to identify host processors and HBAs shown in FIG. 14 was provided by using the utility of FIG. 13, prior to invoking the GUI. Thus, the name of the HBA assigned to a particular HBA can vary, based on the type of operating system used by the host processor to which it is attached. As shown in FIG. 14, host processor cohen  4554   b  communicates with the network using HBA adapter 0 , whereas host processor lo 101239  communicates with the network using two different HBAs, “1f, 0,fca@3,0,” and “1f,0,fca@1,0.” 
     As noted above, in one implementation, dashed grey lines are used to represent paths that connect various devices in the storage network topology view pane  1410 , and black solid lines indicate a selected connection (i.e. a connection between a selected device and another device). In the example of FIG. 14, host processor lo 10239  has been selected in an expanded form, and thus, the path between this host processor, and its two HBAs are shown in solid line form. 
     As may be appreciated from the above description, the storage network topology view pane  1410  allows a user to view the network topology at different levels of granularity. For example, one can view connections from a host processor to a storage system, from a host processor/HBA pair to the storage system, from a host processor to a particular port on the storage system, or from a host processor/HBA pair to a particular port on the storage system. This ability to display different levels of granularity permits one to effectively manage access control in a top to bottom manner, from a host down to its HBA ports and from a storage system down to its ports and storage volumes. Moreover, it permits a user to view the overall topology of a storage network, and then, selectively focus down to a particular set of devices within the network. It should be appreciated that the ability to graphically view a storage topology is particularly useful in larger storage area networks, where the network may include many more network devices than that shown in FIG.  14 . 
     The storage system volumes view pane  1420  graphically illustrates volumes of storage residing on a particular storage system. In one embodiment, the storage volumes view pane  1420  is filled when a network device, such as a host processor, an HBA, a host processor/HBA pair, or a storage system is selected in the storage network topology pane  1410 . The storage volume view pane  1420  shows storage volumes that are available to or reside on the selected network device. The storage system volumes view pane  1420  also graphically depicts other types of information, such as the type of storage volume, whether access rights in a storage volume have been assigned to a particular host processor/HBA pair, whether access rights in a storage volume have been assigned to multiple host processor/HBA pairs, etc. This information is obtained by the GUI accessing the configuration portion  1275  of the configuration database  1232  (FIG.  12 ). 
     Two different types of views are available within the storage system volumes view pane  1420 , i.e., an icon view, or a more detailed view. The icon view displays an icon for each storage volume associated with the selected object. For example, in FIG. 14, an icon is displayed for each of storage volumes  0 - 22  residing on the selected storage system, storage system  0183600314 . Additional storage volumes, if present, may be viewed by expanding the window within which the volumes are shown, or by scrolling downward in a conventional manner. Where multiple storage systems are selected, storage volumes may be sorted by storage system number and then by storage volume, or in any other suitable way. 
     As shown in the storage volumes view pane  1420  of FIG. 14, storage volumes that have been assigned to a selected host processor/HBA pair and storage system/storage port pair are surrounded by a solid line border. For example, storage volumes  3 - 8  are surrounded by a solid line border to indicate that they have been assigned to a particular host processor/HBA pair and storage system/storage port pair that was selected by the user. Where one or more volumes were previously assigned to a particular host processor/HBA pair and storage system/storage port pair, but the assignment has been broken, this may be indicated by a dashed line surrounding the affected volumes. A broken assignment may occur, for example, where an HBA has logged out from the network. Of course, it should be appreciated that other ways of representing the above identified information to a user may alternatively be used, such as using one color to indicate a selected assignment, and another color to indicate a broken assignment. 
     Each storage volume icon in the storage volumes view pane  1420  may shown in one of a number of states. For example, a gray storage volume icon (e.g., storage volume  1530  in FIG. 15) may be used to indicate that the storage volume is available, and that no access rights have been granted for this particular volume. In FIG. 14, storage volumes  0 - 2  and  9 - 22  are displayed in an available state. Alternatively, a storage volume may include highlighted black and white stripes (e.g., assigned storage volume  1535  in FIG. 15) to indicate that the storage volume is owned in a single-path configuration. That is, exactly one host/HBA pair has been assigned access rights to this particular volume. A storage volume can be depicted with a blackened connector bar (e.g., shared assigned storage volume  1540  in FIG. 15) to indicate that the storage volume is a multi-path shared storage volume. That is, two or more hosts/HBA pairs have been assigned access rights to this particular storage volume. In FIG. 14, the icons used to represent storage volumes  3 - 8  indicate that these volumes have been assigned access rights from multiple host processor/HBA pairs. 
     As noted above, a user may select an icon view or a more detailed view of storage volumes. For example, FIG. 16 illustrates a storage volumes view pane  1620  displayed in a detailed manner. As in the storage volumes view pane  1420  of FIG. 14, the representation of each storage volume on the storage system may differ depending on whether access rights have been assigned to that volume, or upon whether a particular storage volume is assigned to a single host processor/HBA pair, or to multiple host processor/HBA pairs. However, the more detailed view of storage volumes can also identify the capacity of each storage volume, an identifier (e.g., name or serial number) of the storage system on which the storage volumes resides, an identifier of which ports on the storage system can access a particular volume, and the owner of that particular volume (i.e., what host processor/HBA pair(s) have access rights to a particular storage volume). It should be appreciated that the present invention is not limited to the information shown in FIG. 16, as different or additional information may alternatively be displayed. 
     As noted above, clicking on a device (e.g., pointing to a particular network device and selecting a particular button on a mouse or other pointing device) highlights path connections associated with that device in the storage network topology view pane  1410 , and fills the storage volumes view pane  1420  with all volumes owned and possibly accessible to or residing on that device. This ability to graphically view a storage area network at varying degrees of detail permits a user to effectively manage access control in a storage network in a hierarchical manner, from a host processor down to its ports. 
     As shown in FIG. 14, the menu bar  1430  is positioned across the top of the management window  1400  in a conventional manner. In one implementation, the menu bar  1430  includes five pull down menus,  1460 - 1480 , each providing the user with a number of options from which to select to perform various tasks. For example, the File pull down menu  1460  can include a run tasks option to execute queued operation such as adding or deleting access of a host/HBA pair to one or more storage volumes. The File pull down menu  1460  can also include a properties option to display or modify properties (e.g., the name of a host or HBA, the name of a storage system or port, etc) of a selected network device, storage system or storage volume, and a report option that generates a report for a selected network device or storage volume. The report option may be used to generate information detailing the configuration of the storage network or the configuration of a particular device or volume, and this information can be either displayed or written to a file. 
     The Edit menu  1465  can provide a user with the ability to modify or delete a queued operation, or to change a login password to the graphical user interface. The View menu  1470  may include an Icon/Details option that permits a user to toggle between icon-based and more detailed view of storage volumes, and a refresh display option that refreshes the work space to reflect storage volume assignments that are currently defined in the configuration portion  1275  of the configuration database  1232 , but have not been updated in the display screen  1400 . The Actions menu  1475  may include various options categorized by the type of device (e.g., a storage system, a storage volume within a storage system, etc.) upon which they act. For example, the Actions menu  1475  can include a bus option that permits a user to define, clear, or swap access rights on a storage system bus, a volume option that adds, removes, or otherwise modifies access privileges to a storage volume, and a storage system option that can be used to perform operations on the configuration database, or to refresh the work space display. The menu bar  1430  may also include a pull down Help menu  1480  that permits a user to display help file, display information about the particular software version of the configuration database code, or graphical user interface software, to set the path to an HTML based browser that is used to view help topics, etc. Other information may be provided using the Help menu  1480 , as the present invention is not limited to the particular topics for which additional information is provided, the organization of such information, or the particular manner in which it can be accessed. 
     The GUI management window  1400  may also include a tool bar  1440  that permits a user to quickly access some of the more frequently used features from the menu bar  1430 . For example, the tool bar may include a properties icon  1405  to display a properties dialog box for currently selected items, a refresh display icon  1415  that reloads volume access assignments from the configuration portion  1275  of the configuration database  1232 , and a run tasks icon  1425  that commits all pending volume assignments for all storage systems, or for a selected storage system. The tool bar  1440  may also include an iconic view icon  1435  that toggles between showing an iconic representation of storage volumes, or showing storage volumes in a more detailed fashion as described above. Similarly, a details icon  1445  may be provided that shows storage volume information in a more detailed tabular format, as in FIG.  16 . The tool bar  1440  may also include a help icon  1455  that displays help files available to the user. It should be appreciated that other ways of providing a quick access to more frequently used features may also be provided, as the present invention is not limited to the particular implementation shown in FIG.  14 . For example, a sequence of keyboard commands (e.g., “control F”) may be used instead, or in addition to a tool bar. 
     The status bar  1450  is positioned across the bottom of the window  1400  and provides informational messages relating to current actions selected from the menu bar  1430  and the tool bar  1440 . For example, the left hand side of the status bar  1450  can indicate whether tasks are pending or completed, with the right hand side indicating the number of current tasks in the task list. Other ways of providing this information may alternatively be used, as the present invention is not limited to the particular implementation of the status bar  1450  shown in FIG.  14 . 
     FIG. 17 illustrates a storage network topology pane  1710  for a storage network that includes a number of different host processors as well as a number of storage systems. Each of the host processors except the host processor “pablo” is shown in a collapsed form. Host processor pablo is shown in an expanded form, illustrating the path connection between the host processor pablo, the HBA port FcaPort 2 , and the storage system  9000003077 . Storage system  900003078  is illustrated in a collapsed form, whereas storage system  9000003077  is illustrated in an expanded form, revealing each of the storage system port adapters accessible from the network. 
     An exemplary description of the manner in which access control can be configured for a relatively simple storage area network is now described with respect to FIGS. 18-22, and  14 . FIG. 18 illustrates the storage network topology in which access rights to particular storage volumes will be provided for two different host processor systems, host processor cohen 4554   b  and host processor lo 10239 . More particularly, FIG. 18 illustrates a management window  1800  that would be seen by a user after running a utility similar to that described in FIG. 13, such as the VCMFIND utility, on each of host processors cohen 4554   b  and lo 10239 , and then executing the GUI on administrator host cohen 4554   b . In this example, host processor cohen 4554   b  will be granted shared access to storage system  0183600314 , storage volume  4 , from HBA adapter 0  on host processor cohen 4554   b . Host processor lo 10239  will be granted access to storage system  0183600314 , storage volumes  3  and  5 - 8  , from HBA adapter 1  on host processor lo 10239 , and will be granted shared access to storage volume  4 , from HBA adapter 2  on host processor lo 10239 . In FIG. 18, the user selects the storage system  0183600314  and expands the storage system icon to show all the storage adapter ports connected thereto. The result of these actions are shown in FIG.  19 . 
     By expanding and selecting storage system  0183600314 , the volumes view pane  1920  is filled in with all storage volumes residing on this storage system. As can be seen by the type of icon used to represent the storage volumes in the volumes view pane  1920  of FIG. 19, none of the volumes of storage system  0183600314  have been assigned to a host processor. Furthermore, by expanding the storage system icon, the storage adapter ports residing on the storage system  0183600314  are displayed. Gray path connection lines are drawn from each storage system port to each host on the storage network that can connect thereto. As shown in storage network topology pane  1910  of FIG. 19, the storage adapter ports residing on storage system  0183600314  include Fibre Channel adapter ports (Fa) Fa 14   a , Fa 14   b , Fa 15   a , Fa 15   b , Fa 16   a  and Fa 16   b . The selection of storage system  0183600314 , (for example, by clicking on the storage system icon using a mouse or other pointing device), results in the icon for storage system  0183600314  becoming highlighted. In addition, the selection and expansion of the icon for storage system  0183600314  results in grey path lines being drawn between each storage system port on the selected storage system and the selected storage system (not shown). By selecting a particular port that is attached to the storage system (e.g., port Fa 15   a ), the selected port becomes highlighted and the gray path lines from the storage system to the selected port become darkened (not shown). After selecting a particular storage system, all volumes on that storage system are displayed in the volumes view pane of the management window. 
     To configure access to storage volume  4  on port Fa 15   a  from HBA adapter 0  of host processor cohen 4554   b , the user then selects host processor cohen 4554   b  by selecting the appropriate icon. Upon selection, host processor cohen 4554   b  becomes highlighted and the formerly gray line from host processor cohen 4554   b  to storage port Fa 15   a  becomes solid black. By selecting the expanded form of host processor cohen 4554   b , (for example, by clicking on the plus sign in the host processor icon), the HBAs that are connected to host processor cohen 4554   b  are displayed. The results of the preceding actions are shown in the storage network topology pane  2010  of FIG. 20, in which host processor cohen 4554   b  is connected by a solid black line to a HBA adapter 0 . 
     To select storage volume  4  for allocation to host processor cohen 4554   b /adapter 0 , the user simply selects storage volume  4  icon. This is shown in the volumes view pane  2020  of FIG.  20 . After selecting a particular volume, the user may select the actions pull-down menu  2075  and select an option, such as add access. The result of these steps is to add access to storage volume  4  on storage system port Fa 15   a  from HBA adapter 0  on host processor cohen 4554   b . Similar steps may be performed to add access to storage volume  4  on storage system port Fa 15   b  from HBA adapter 0  on host processor cohen 4554   b . In one embodiment, after these steps are performed, a task list such as shown in FIG. 21 is displayed for the user. As shown in the task list of FIG. 21, access to volume  4  has been added from HBA adapter 0  on host processor cohen 4554   b  to storage system adapter ports  15   a  and  15   b . The user selects the confirm button shown at the bottom of the task list to confirm this task. It should be appreciated that the task list is not required. However, in one embodiment, by providing a user with the results of their assignments and requiring their confirmation, inadvertent changes can be reduced. Furthermore, it should be appreciated that the specific steps used to configure access for host processor cohen 4554   b  and the order in which they are performed can vary, as the present invention is not so limited. 
     FIG. 22 illustrates a graphical management window  2200  showing the assignment of storage volume  4  in volume view pane  2220  that a user would be provided with after performing the above steps. As noted previously, the selected storage volume in the volumes view pane  2220  may be enclosed by a border to indicate that this volume has been selected. Moreover, because this storage volume is now allocated to a particular host processor/HBA pair, storage volume  4  is represented by an assigned storage volume icon (i.e. assigned storage volume icon  1435  in FIG.  15 ). Furthermore, it should be noted that the paths shown in the storage network topology pane  2210  between host processor cohen 4554   b  and HBA adapter 0  and storage volume  4 , via either of the storage system port adapters  15   a  and  15   b , are shown in dark lines. 
     A similar procedure may be used to set up shared access to storage volume  4  from HBA adapter 2  of host processor lo 10239  and set up access to storage volumes  3 , and  5 - 8  from HBA adapter 1  of host processor lo 10239 . The resultant display after the management window has been refreshed is shown in FIG. 14, described previously above. 
     It should be appreciated that after the preceding steps, the assignments of storage volumes to each of host processors cohen 4554   b  and lo 10239  have not been made permanent in the configuration portion  1275  of the configuration database  1232  (FIG.  12 ). To make these assignments permanent in the configuration portion  1275  of the configuration database (i.e., so they will persist across power cycles of the storage system on which the configuration database resides), the user executes the run task command in the File menu bar. This extra step helps to prevent inadvertent changes from being made to the configuration database  1232 . In one embodiment of the present invention, execution of the run task command is protected by a password so that tasks cannot be executed by an unauthorized user. 
     According to another embodiment of the present invention, a CLI based user interface is provided to manage network devices and manage and assign storage volumes to network device in a storage network. As in the GUI based user interface described above, the CLI based user interface communicates with a configuration database  1232  on a storage system  1220  to manage network devices and manage and assign storage volumes thereto. One exemplary implementation of a CLI based user interface, called FPATH, is described in great detail in the publication entitled, EMC Volume Logix Product Guide, as noted above. It should be appreciated that embodiments of the present invention directed to a CLI based user interface are not limited to the particular implementation of the FPATH CLI described therein, as the CLI based user interface of the present invention may be implemented in many different ways. In one embodiment of the present invention, the CLI based user interface is implemented in software and can be executed on a CPU  1240  of a host processor  1212 ,  1214 . The CLI permits network devices and storage volumes in a storage system to be managed using a WWN or, alternatively, using an AWWN that can be assigned to a particular network device. 
     According to one embodiment, the CLI based user interface includes a set of commands having the format “COMMAND action {arguments}, where COMMAND is a name of the executable CLI, for example “FPATH”, and where actions are subcommands that can be used to update the configuration database  1232  or display configuration information that is maintained in the configuration database  1232  of a storage system. Actions that may be performed on the configuration database  1232  of a storage system  1220  include initializing the configuration database  1232 , adding or removing a network device such as a host, HBA or host/HBA pair to the configuration database  1232  so that network devices can access storage volumes on the storage system, adding or removing access to a particular storage port that a host/HBA pair can access on the storage system, and adding or removing access to a particular volume that a host/HBA pair can access on the storage system. 
     Other actions that may be performed using the CLI based user interface include backing up the configuration database  1232  maintained by the storage system  1220  to a specified file, restoring the configuration database  1232  from the contents of such a backup file, providing an alias for a particular host/HBA pair that can be used in managing and configuring network devices on the storage network, etc. Display actions available using the CLI can include displaying information relating to the manner in which network devices are related in the storage network. This information can include what devices are currently logged into a storage system, what access rights to storage volumes these network device have on the storage system, etc. This reporting information can be displayed on a display screen of a host processor, or saved to a file. It should be appreciated that the present invention is not limited to the particular set of actions described above, as other actions, or additional actions may alternatively be provided. Advantageously, the CLI based user interface may be used in conjunction with a utility such as that described above with respect to FIG. 13 to manage network devices using more meaningful identifiers than their WWN. The CLI based user interface can thus have similar functionality to that described above for the GUI user interface. Accordingly, as the implementation of a CLI would be readily understood from the description of the GUI based user interface discussed above, further details of the CLI based user interface are omitted herein. 
     Having described several embodiments of the invention in detail, various modifications and improvements will readily occur to those skilled in the art. Such modifications and improvements are intended to be within the spirit and scope of the invention. Accordingly, the foregoing description is by way of example only, and is not intended as limiting. The invention is limited only as defined by the following claims and the equivalents thereto.