Abstract:
A system is described in which a plurality of host computers are coupled to a storage system for storing and retrieving data in the storage system. The storage system includes individually addressable units of storage such as volumes or logical unit numbers. A security management system controls access to each of the individually addressable units of storage based upon the identification of the host permitted to access that unit of storage.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     This invention relates to storage area networks, and in particular, to security of data in such storage area networks.  
         [0002]     Storage area networks (SAN) are now widely deployed around the world to provide storage facilities for computing environments. The consolidation of storage into large facilities allows for more efficient administration and control, and enables the provision of highly reliable backup and redundancy systems to dramatically limit data loss from system failures or natural catastrophes. The benefits of such storage have caused a dramatic increase in its use throughout the world.  
         [0003]     Storage area networks are designed to allow access from many different host systems so the data may be reliably retrieved and stored from different locations under the control of different processors. Such storage and retrieval is often carried out over public networks, such as the internet.  
         [0004]     To more effectively enable access to the storage system, it is usually configured into smaller portions which can be allocated to different processors or other resources requiring the storage. For example, conventional storage systems include a large number of hard disk drives, with each hard disk drive itself including many gigabytes of storage. One way to divide the storage resource into smaller portions is to create Logical Units that are assigned a unique Logical Unit Number. Each LU itself consists of a numeric address, thereby permitting the large storage system to appear as many smaller storage units to the host computers accessing them, enabling more efficient operation.  
         [0005]     The LUs are typically assigned to hosts so that a particular LU may be accessed only by designated hosts which have “permission” to access that portion of the storage system. This provides enhanced security as the software controlling access to the storage system will only permit access by certain previously defined hosts. While it is somewhat arbitrary how many hosts are permitted to access a given LU, conventionally only one host usually has access rights to a given LU at a given time. In this manner the data on the LU is protected against access by hosts or servers other than those previously designated, thereby enhancing the security of the data.  
         [0006]     The SAN itself usually consists of one or more disk array devices, for example configured under a selected RAID protocol, with multiple host devices connected by fiber channel switch network devices or other well known means to the storage area network. Inside the architecture, host computers run cluster management software to negotiate with each other to determine which hosts “own” which portions of the storage or LUs. A commonly known “failover” function enables the clustered architecture of the SAN to be highly available. In a failover situation, a failure occurs, but is made relatively transparent to the user of the system by transferring operations that were running on one node to another node or nodes within that cluster of nodes.  
         [0007]     The hosts and SAN are configured in a clustered environment in which more than one host has access to a given SAN. The host is typically a computer, for example an application server or a database server. The traditional clustering software used to provide this configuration has a limitation in that a portion of the storage, for example, an LUN, must be configured to allow I/O access from all host nodes in the cluster. For example, if host node A is running an application X, and they are in the same cluster, it is desirable that if host A fails, the task of application X be taken over by another host B. When this happens the LU security for applications must be set to allow I/O access from both hosts A and B. If such multiple access is routinely provided by the set-up program at system initialization, however, it can be a cause of data corruption resulting from the wrong access of the data.  
         [0008]     This invention provides an improved method and system for security in such an environment by enabling dynamic changes in the LU security to allow a different host to access a particular portion of the storage after a failure, when that host could not have accessed that portion of the storage before the failure.  
       BRIEF SUMMARY OF THE INVENTION  
       [0009]     The system of this invention is particularly applicable to host nodes which are configured in a cluster system. During the initialization of such a system, the host computers negotiate to gain ownership to access the data storage resources which are divided on the basis of LUs (or volumes or other units). Each LU is then configured to permit and reject I/O accesses by hosts, typically based on IDs assigned to the hosts, such as WWN, port ID. In the primary security configuration, one LU may allows I/O access only from one host.  
         [0010]     According to this invention, if a problem occurs in the primary host group (assigned to the particular LU), another host group takes over execution of that process to continue system activity. At the time this occurs, the cluster management software running on the host detects the change in ownership and notifies the storage device that ownership for that LU has been changed. The LU security function in the storage device then dynamically changes its security configuration to allow I/O accesses from the new host. As a result, this invention provides improved security. Secondary hosts within the cluster that run the application processes are thereby not permitted to access the LU until they have obtained that right, typically as a result of a failure in the primary host. While operating in this manner, data corruption at the LU level is greatly reduced, and access of that data by unauthorized applications in generally prevented.  
         [0011]     In one embodiment in a system having a first host computer, a second host computer, and a storage, and in which access to at least a portion of the storage is controlled to permit access to the storage by the first host, and prevent access to the storage by the second host, a method of changing the authorization for access to the storage includes informing the security system of a negotiation between the hosts and restricting access to the portions to the host that acquired such access in the negotiation. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1  is a block diagram illustrating an in-band system implementation;  
         [0013]      FIG. 2  is a block diagram illustrating an out-of-band system implementation;  
         [0014]      FIG. 3  illustrates a sample data structure for storage configuration information;  
         [0015]      FIG. 4  illustrates a sample data structure for security configuration information;  
         [0016]      FIG. 5  is a flowchart illustrating one embodiment of the method of this invention;  
         [0017]      FIG. 6  is a diagram illustrating an ownership change message; and  
         [0018]      FIG. 7  is a diagram illustrating an access control status change message.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0019]      FIG. 1  is a block diagram illustrating a typical system configuration for a storage area network. As illustrated, the overall system includes a first host device  108 A and a second host device  108 B. These host devices are typically computers or application servers of well known design. The hosts are coupled to a storage system  109 , typically made up of a disk array, for example configured in accordance with a RAID protocol. The disk array  109  typically includes a large number of disk drives  106 , of which one is illustrated. Disk  106  has been configured to have two volumes  105 A and  105 B.  
         [0020]     The hosts  108  and storage system  109  are coupled together using a suitable means for exchanging data between them. A data link  110  is illustrated in  FIG. 1 . The data link  110  can take any appropriate format, for example, a fibre channel network, a local area network, the internet, a private network, a network switch device, or any other interconnection means.  
         [0021]     In a typical storage system  109 , large numbers of storage volumes such as  105 A and  105 B will be provided. The storage volumes  105  themselves, or even portions thereof, are given logical unit numbers (LUNs) or other identification to identify them and/or provide addressing information for the addressing of information to be stored in those storage volumes, or retrieved from those storage volumes. The storage system  109  and the hosts  108  each include an interface  107  to provide an interface to the network. Interface  107  conventionally is provided by using a host bus adapter (HBA) or a gigabit Ethernet card, or other known interface. The selection of any particular interface will depend primarily upon the configuration of the data link  110  to which it is coupled.  
         [0022]     Each of the hosts includes cluster management software  102  which operates on that host. The cluster management software in each host is coupled to similar software in other hosts. For example, as shown in  FIG. 1 , the cluster management software  102 A operating on host device  108 A is coupled to communicate with the cluster management software  102 B operating on host  108 B. The cluster management software communicates with the corresponding software on other hosts to determine the ownership of storage volumes  105  for a particular host. Each storage volume  105  can be accessed by one or more computers that have the ownership for the volume. During initialization of the system, the hosts receive the LUNs, and, either independently, or with support from a system operator, the hosts decide which LUNs are to be associated with each host. After this has been determined, the volume security control software  101  requests the storage device  109  to allow I/O accesses from that host to the designated volumes  105 . Once the system has been appropriately initialized, then the security management program  103  in storage system  109  controls access to the storage volumes  105 . The security management program stores the security configuration information  104  in a protected area for later use.  
         [0023]     The system illustrated in  FIG. 1  is often termed an “in-band” control system.  FIG. 2  illustrates a different control system referred to as an “out-of-band” control system. The storage system  109  is the same in  FIG. 2  as that described in  FIG. 1 . In contrast, however, the architecture of the system illustrated in  FIG. 2  places the responsibility for volume security control on a storage manager  112 . Storage manager  112  is coupled to each of the hosts, and is responsible for the volume security control software  101 . This software provides the same functionality as the volume security control software  101  provided in the system configuration shown in  FIG. 1 . The volume security control software  101  running on the storage manager  112  coordinates management of the volume security. It also monitors the storage system and stores information about the configuration of the storage system and the like in local storage  111 .  
         [0024]      FIG. 3  is a diagram illustrating the data structure for storage configuration information  111  (shown in  FIG. 2 ). This diagram illustrates how access is controlled to various portions of the storage. In  FIG. 3  to provide an example, volumes  2 ,  3  and  4  are shown in the column “Volume ID.” Each volume is allocated to one or more ports to be activated. As shown by the diagram, volumes  2  and  3  are allocated to port  0 , while volume  4  is allocated to port  1 . The storage ID shown in  FIG. 3  is a storage identification parameter. This parameter identifies the storage asset, usually by serial number, node World Wide Name, or vendor-specific identification number. The node World Wide Name is a fixed, unique address that is assigned to disk array device  109 . In  FIG. 3  the storage ID is shown as “Array #0” representing the first disk array associated with the storage product. The interface identification number (port 0 or port 1) represents the unique identification associated with a given network interface. Alternatively, the port WWN, or Port ID which are assigned to each port can be used to provide this information. The port WWN is a fixed, unique address that is assigned to each port. The port ID is an unique identifier that is assigned to each network interface hardware. Also, IP address or MAC address can be used if I/F  107  is a Ethernet card.  
         [0025]     The host identification (“Host ID” in  FIG. 3 ) represents an identifier to designate a host that is permitted or restricted to access the particular designated volume (in that row of the table). The LUN security function uses the node WWN of the host, or the port WWN of the HBA, or the MAC address of the network card installed on the host to provide this identification parameter. To illustrate its operation,  FIG. 3  shows the hypothetical example that volume  3  on port 0 of array 0 is allowed to be accessed by hosts  8  and  9 , but access is not permitted for host  12 .  
         [0026]      FIG. 4  is a diagram illustrating an example of the data structure for the security configuration information  104  found in disk array unit  109 . As shown by  FIG. 4 , this data structure is synchronized with, and corresponds to, the storage configuration information  111  from the management unit  112 . As also illustrated, the storage ID is not required since this information is maintained in the storage unit itself (as identified by  FIG. 3 ).  
         [0027]      FIG. 5  is a flowchart illustrating a preferred embodiment of the method of operation of this invention. The diagram shown in  FIG. 5  is divided into two parts—operations that occur within the host (on the left of the diagram), and operations that occur within the disk array (skewed to the right of the diagram). The process begins with step  501  in the host in which cluster management software negotiates to determine the ownership or control of the disk resources. With reference to  FIG. 1 , this step is carried out by the software  102 A in host  108 A negotiating with the software  102 B in host  108 B. Such a negotiation typically uses the known SCSI-3 persistent reserve algorithm, or the SCSI-2 challenge/defense protocol. At the conclusion of the process, the host computers will have rights to access particular LUNs (or volumes) in the disk array.  
         [0028]     Step  502  in  FIG. 5  illustrates that the negotiation concludes with the cluster management software notifying the volume security control software of the results of the negotiation. The volume security control software  101 , as described in conjunction with  FIGS. 1 and 2 , will reside either in each of the hosts ( FIG. 1 ) or in a manager ( FIG. 2 ).  
         [0029]      FIG. 6  is an illustration of an ownership change message sent by the cluster management software  102  to the volume security control software  101 . As shown in  FIG. 6 , the hypothetical message illustrates that volume number  2  has been acquired by host number  8 , and that volume number  3  has been lost to host number  8 .  
         [0030]     Returning to the process illustrated in  FIG. 5 , after sending the message, at step  503  the volume security control software  101  will request the disk array  109  to change the configuration for volume security. This is carried out by the volume security control software  503  sending a request message to the security management program  103  found in the disk array  109 . This message requests changes in the LUN (or volume) security configuration.  
         [0031]      FIG. 7  illustrates a typical message sent by the volume security control software  101  to the security management program  103 . As shown in  FIG. 7 , an access control status change message is being transferred to illustrate that host number  8  is now permitted to access volume number  2  and is no longer permitted to access volume number  3 .  
         [0032]     Again returning to  FIG. 5 , once the message of  FIG. 7  is received by the security management program  103 , it carries out step  504  in  FIG. 5 . At this time the security management program  103  reconfigures the LU security settings and updates the security configuration information  104 . This operation will result in new entries in the security configuration information table (shown in  FIG. 4 ) by which the status for volume number  2  and host number  8  is changed from “deny” to “permit.” Similarly, the status for volume number  3  and host number  8  is switched from “permit” to “deny.” 
         [0033]     Following the disk array device operation of step  504 , the host device carries out step  505 . In this step the cluster management software maintains control of the disk resources to verify that no inconsistent status has occurred. This is typically carried out using a “heartbeat” communication protocol. As shown by step  506  in  FIG. 5 , if the heartbeat is lost, or if an inconsistent status is detected, then the cluster management software  102  will reset the system and restart the negotiation process to allocate disk resources to hosts.  
         [0034]     The foregoing has been a description of preferred embodiments of this invention. It should be appreciated that departures from the specific embodiment illustrated may be made while remaining within the scope of this invention. For example security for the storage devices may be implemented on the basis of other than LUs or volumes, instead using addresses or other designations. The scope of the invention is defined by the appended claims.