Patent Publication Number: US-6671776-B1

Title: Method and system for determining and displaying the topology of a storage array network having multiple hosts and computer readable medium for generating the topology

Description:
RELATED APPLICATION 
     The present application is a continuation-in-part of U.S. Ser. No. 09/431,715 entitled “Method and System For Partitioning a Storage Array in a Storage Array Network,” filed Oct. 28, 1999 which is hereby incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention is directed to storage array technology, and, more particularly, to storage array technology that automatically determines the topology of a storage array network including the association of host port adapters, hosts and cluster groups. 
     BACKGROUND OF THE INVENTION 
     Although still an evolving, Storage Area Networks (SANs) promise to revolutionize the majority in which storage are coupled in the years to come. Today, the vast majority of host systems are directly attached to the storage that they use. With storage area metworking, storage and hosts will no longer be so closely coupled. Instead, system architects will be able to engineer configurations that answer some requirements and, in the future, will be able to answer even more of the myriad of requirements that have, to date, been only answerable by proprietary storage solutions. 
     SANs offer system designers a whole new way of approaching storage. Traditionally, the host-storage interface has been closely coupled. In fact, the only time that small computer system interface (SCSI) storage has been successfully attached to multiple hosts is in the case of clustered central processing units. The reason for this is simple, the SCSI protocol was not developed with the idea of multiple heterogeneous hosts sharing the same SCSI cable. Because SCSI has been relatively limited in its speed and the ability to address a large amount of disk capacity on SCSI does not exist, the idea of sharing storage between a number of hosts on the SCSI interface has not traditionally been a driving factor. 
     There are a number of reasons why end users see value in sharing storage between a number of hosts. One of the primary reasons is that the investment in storage can be amortized across multiple hosts. This is an important consideration today, since the expense of storage is a significant factor in the cost associated with a system installation. This is particularly true in cases where multiple small capacity hosts require highly available storage such as Redundant Array of Independent Disks (RAID). Another factor is storage consolidation. By enabling a variety of hosts to attach to a single, large array, management and maintenance costs are reduced, positively impacting the total cost of storage ownership. A third factor is standardization. Instead of forcing system administrators to work with storage arrays from multiple vendors, standardization provides a single, centralized management system capable of managing storage throughout the SAN. 
     One approach to creating a shared SAN is the use of specially developed access control software run on the storage array itself. This software controls host access to storage within the array on a logical unit number (LUN) basis, based on the actual fibre channel address of the host. Essentially a table driven access control, this solution is able to map host access requests to storage associated with that host exclusively or inclusively, depending on the configuration and application requirements. In essence, the host only sees what the access control software on the array allows it to see, removing from its view all other storage in the array. For example, it can be possible to share a 1TB RAID array across ten hosts, each of which believes the array only has 100GB of capacity. By implementing management of the software control in the array&#39;s storage management utilities, the solution can be made fully host independent. 
     A disadvantage in today&#39;s SCSI and fibre channel storage connect environment is the inability to automatically determine the topology of a network and convey that topology to a system administrator, for example, in a user-friendly manner. Currently host port adapters are provided with a unique identification (I.D.), such as a worldwide name (WWN). This information is transmitted to a storage array controller to identify the adapter through which a command was issued. Unfortunately, if a host has multiple adapters, information concerning the host is not conveyed. Thus, apart from manually checking, there is no way to know what adapter is associated with what host. Moreover, if hosts are grouped in clusters, associating an adapter with a cluster is not automatically possible. Without this information, it is very time consuming to determine the topology of the network. Currently, to provide a system administrator with information concerning the topology of a network, a mapping of the host port adapters to the hosts and clusters must be done manually. This is a time consuming proposition as storage array networks become more complex and is prone to errors. In addition, if changes are made to the topology of the network such as replacing a failed adapter, the administrator must manually map the WWN of the replacement adapter into the existing topology. Thus, the topology reflected to the administrator can become outdated without the administrator&#39;s knowledge. 
     It is thus desirable to provide an automated method and system for determining the topology of a storage array network and conveying that topology to an administrator in a user friendly fashion. It is also desirable to provide a method and system for automatically updating the topology whenever changes are made to the topology. It is also desirable to provide an administrator with a view of the current topology at a remote location from which the administrator can make changes to the topology. 
     SUMMARY OF THE INVENTION 
     According to a first aspect of the invention there is provided a method of transmitting information from which a topology of a storage array network having multiple hosts, with at least one host having a plurality of host port adapters, may be determined. The method includes the steps of: 
     (a) generating a command from a host wherein the command includes a unique host identifier and a unique host port adapter identifier wherein the unique host identifier is linked to the unique host port adapter identifier; and 
     (b) transmitting the command from the host to a controller of a storage array network through a first path coupling the host port adapter to the controller. 
     According to a second aspect of the invention, there is provided a storage array network including: 
     a plurality of hosts; 
     a storage array having multiple volumes; 
     a storage array controller operatively coupled to the storage array; 
     a bus operatively coupling each host to the storage array controller, 
     wherein each of the plurality of hosts transmits to the storage array controller a command that includes a unique host identifier and a unique host port adapter identifier. 
     According to a third aspect of the invention, there is provided a computer readable medium for generating a topology of a storage array network. The medium includes: 
     code that represents a table of unique identifiers of a plurality of hosts and unique identifiers of a plurality of host port adapters associated with each of the plurality of hosts; and 
     code that utilizes the table to generate a display of the topology of the network. 
     According to a fourth aspect of the invention, there is provided a system for determining a topology of a storage array network having multiple hosts with at least one host having a plurality of host port adapters, the system comprising: 
     a general purpose computing device; and 
     a computer program comprising one or more program modules executable by the computing device; 
     wherein the program modules comprises a table module for uniquely associating each host and its host adapter port with a controller via a path and a topology module that utilizes the table module to generate a topology of the network. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates a data storage system according to a preferred embodiment of the present invention. 
     FIG. 2 is a schematic illustration of the definitions given in Table 1. 
     FIG. 3 is a schematic of a SAN storage consolidation according to a preferred embodiment of the present invention. 
     FIG. 4 is a schematic diagram of a topology according to a preferred embodiment of the present invention. 
     FIG. 5 is a schematic diagram of a multiple cluster, single port controller, redundant path topology. 
     FIG. 6 illustrates a screen that can be displayed on the management console to display the configured topology of the SAN to a system administrator. 
     FIG. 7 is a display screen that can be displayed at the management console for partitioning storage in a storage array network. 
     FIG. 8 is a display screen defining a user interface that can be displayed on the management console that allows a user to create a new volume. 
     FIG. 9 is a block diagram of control logic according to a preferred embodiment used to access the SAN. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 illustrates a data storage system  100  according to a preferred embodiment of the present invention. A host system  102  or server is coupled by host adapters  104  and  106  to storage arrays  108  and  110  by host buses  112  and  114 . While the host system  102  is preferably a personal computer (or “PC” type) or server computer system, it should be clearly understood that the present invention is equally suitable for use with other computing environments not specifically disclosed herein including mainframe computers, minicomputers and SAN bridges. In a preferred embodiment, the host system  102  includes at least one ×86 microprocessor and acts as a server in a distributed computing environment. The host buses  112  and  114  are preferably well-known SCSI buses. Alternatively, other bus architectures may be employed in embodiments of the invention, including without limitation fiber channel or Peripheral Component Interconnect (PCI). 
     RAID controllers  116 ,  118 ,  120  and  122 , preferably represent low end RAID controllers operatively coupling a host adapter (e.g., host adapter  104 ) to a storage array, such as storage array  108 . Intervening devices or interconnections may also be disposed between the host adapter and the storage array. In an alternative embodiment, each RAID controller in the data storage system may be replaced with PCI RAID controllers or other low end RAID controllers. 
     In the illustrated embodiment of FIG. 1, RAID controller  116 , for example, preferably provides a level of RAID functionality, disk caching, and environmental monitoring. The RAID controller  116  presents its own volumes to the host adapter  104  and maps logical units numbers (LUNs) appropriately to the data stored in storage array  108  as will be described in detail hereinafter. In a typical scenario, the RAID controller  116  “stripes” a volume across all five storage disks of disk arrays  124  and  126  to provide RAID  0  functionality as is well known. RAID controller  118  presents volumes mapped to disk arrays  124  and  126  to provide dual access to the storage arrays. In a similar manner, the RAID controller  120  presents volumes mapped to disk arrays  128  and  130 . Controllers  120  and  122  are redundant controller pairs as are controllers  116  and  118 . 
     FIG. 1 also illustrates an example of redundant controllers. That is, a drive in array  126  may be accessed by either controller  116  or  118 . Therefore, if one or the other controller fails, a host system may still access the drive through the remaining controller. 
     It can be difficult for a system administrator to manage a complex storage area network without having access to the topology of the network. The present invention provides a dynamic method and system for automatically determining the topology of a storage array network. This makes it possible for a network. In addition as changes are made to the topology of the network, the present invention automatically changes the generated topology to reflect those changes and present the administrator with a most current view of the network&#39;s topology. 
     For the purpose of clearly describing the present invention, it is helpful to define several terms in Table 1 below and with reference to FIG.  2 . 
     
       
         
           
               
               
             
               
                   
               
             
            
               
                 Logical Unit 
                 A “Logical Unit Number” (LUN) is redefined from its 
               
               
                 Number (LUN) 
                 customary meaning to be part of the addressing 
               
               
                   
                 mechanism that is used by the host to access the 
               
               
                   
                 volume. The association between the LUN and the 
               
               
                   
                 volume is arbitrary for a HOST ID - Controller Port 
               
               
                   
                 Storage path. The LUN can be assigned by 
               
               
                   
                 an administrator configuring the storage array 
               
               
                   
                 as will be described hereinafter. 
               
               
                   
               
            
           
         
       
     
     FIG. 3 is a schematic of a SAN storage area network  200  according to a preferred embodiment of the present invention. The storage area network  200  includes a plurality of nodes  202 - 214  operatively coupled to a storage array  216 . At each node is a host or server that is operatively coupled to the storage array  216 . Nodes  202  and  204  are grouped together as a first cluster  218  and nodes  210  and  212  are grouped together as a second cluster  220 . The storage array  216  is represented logically as having eight he volumes that are coupled to the nodes. 
     A management console  222  is coupled to the storage array  216  preferably by a network  224 . Network  224  may be an Ethernet, LAN, or the World Wide Web, for example. In a preferred embodiment the management console  222  is LSI&#39;s Logic SyMsm 7  Enterprise Storage Manager. The management console  222  utilizes Java based software and has a web-based graphical user interface running on a browser such as Microsoft Internet Explorer or Netscape&#39;s Navigator. SyMsm7 is a trademark of LSI Logic Corporation of Milpitas, Calif. Internet Explorer is a trademark of Microsoft Corporation of Redmond, Washington. Navigator is a trademark of Netscape Corporation of Mountain View, Calif. 
     Using the management console, a system administrator, for example, can provide on-line administration to allow configuration, maintenance, reconfiguration and performance monitoring of the storage area network. In a preferred embodiment, a user is provided with two views of the storage array network through the management console  222 . The first view is an enterprise storage array discovery and monitoring view which provides a way for discovery and gross level monitoring of the storage arrays that are part of the identified enterprise configuration. The second view is a storage array management view which allows for the configuration and monitoring of a particular storage array. The storage array management view is used to partition the storage according to a preferred embodiment of the present invention as will be described hereinafter. The management console  222  may be connected to the storage array network either directly as shown or through the hosts themselves. Alternatively, the management console manager may be resident on one or more of the hosts attached to the storage array network. Regardless of where the management console resides, the manager will provide a description of the entire storage array network including storage partitioning volume mappings as will be described in detail hereinafter. 
     FIG. 4 is a schematic diagram of a topology  400  according to a preferred embodiment of the present invention. The topology includes four hosts  402 - 408  and two controllers  410 ,  412 . Hosts  402  and  404  are grouped in a first cluster  401 . It will be appreciated that the topology of a network may includes more than four hosts, two controllers and one cluster and the present invention is not limited to the particular embodiment illustrated. In this preferred embodiment, each controller has a first port and a second port. All of the hosts except host # 2  ( 404 ) have a single host port adapter (HPA). The storage array  414  has five volumes associated therewith. The hosts are configured so that host # 1  ( 402 ) has access to the volume “Sarah” through the first port of the first controller  410  at LUN O as well as access to the volume “Bob” through the first port of the first controller  410  at LUN  8 . Host # 2  ( 404 ) has two host port adapters. The first port adapter HPA # 1  has access to the volume “Bob” through the second port of the first controller at LUNO. 
     In addition, the same path is used to access the volume “Sarah” at LUN  1 , “Kim” at LUN  2 , and “Bill” at LUN  3 . The second host port adapter of Host # 2  ( 404 ) has access to the volume “Bill” through the first port on the second controller at LUN  0 . In addition, the same path is used to access the volume “Sue” at LUN  1 . Table 2 below illustrates the five different host ID-controller port storage paths shown in FIG.  4 . 
     In addition, clustering information may also be conveyed. For example, some clustering software supplies cluster name information that can be transmitted to the storage array controllers and input into the data maintained by the controllers which is used to dynamically generate the topology of the network. Alternatively, cluster information can be entered manually as is well known. 
     
       
         
           
               
               
               
               
               
               
             
               
                   
               
               
                   
                   
                   
                 Controller 
                   
                 Volumes Assigned to 
               
               
                 Host 
                 HPA 
                 Controller # 
                 Port # 
                 Storage Path Name 
                 LUN # 
               
               
                   
               
             
            
               
                 #2 
                 #1 
                 #1 
                 #2 
                 Host #2 ID-Controller #1- 
                 Bob to LUN 0 
               
               
                   
                   
                   
                   
                 Port #2 
                 Sarah to LUN 1 
               
               
                   
                   
                   
                   
                   
                 Kim to LUN 2 
               
               
                   
                   
                   
                   
                   
                 Bill to LUN 3 
               
               
                   
               
            
           
         
       
     
     As can be seen in FIG. 4, in the case of the volume labeled ‘Bob’, both Host # 1  and Host # 2  have access to ‘Bob’ through the same controller, but through different ports and at different LUN addresses in that Host&#39;s address space. This may be useful if volume ‘Bob’ is a boot disk for one of the two hosts, but is not the boot device for the other. Host # 3  and Host # 4  are attached to the storage subsystem using the same controller port, but each has its own LUN address space, i.e. Host # 3  is assigned only volume ‘Kim’ at LUN  0 , whereas, Host # 4  is assigned ‘Sue’ at LUN  1  and ‘Kim’ at LUN  7 . This may be useful in allowing each host to address the volumes it needs to access without taking up a LUN slot for a volume it does not, or should not, need to access. This is also useful to provide security to prevent one host from inappropriately seeing data of another host. Host # 2  is the only host in the example with multiple ports into the storage subsystem. In this case, the first interface is labeled storage path ‘Host # 2  ID—Controller # 1  Port # 2 ’ connecting the host to the first controller&#39;s second port. The second interface to the storage subsystem is labeled storage path ‘Host # 2  ID—Controller # 2  Port # 1 ’ connecting the host to the second controller&#39;s first port. Each storage path is provided its own Logical Unit Address Space. Storage path ‘Host # 2  ID—Controller # 1  Port # 2 ’ has been assigned volume ‘Bob’ at LUN  0 , while storage path ‘Host # 2  ID—Controller  2  Port # 1 ’ has been assigned ‘Bill’ at LUN  0  and ‘Sue’ at LUN  1 . Host # 2 , HPA # 2  has also been assigned Sarah @ LUN  1 , Kim @ LUN  2  and Bill @ LUN  3 . This may be useful in providing multiple paths to the same storage for the server, thus avoiding single points of failure other than the server itself. In Table 2, the host #ID represents the world wide name of the HPA that uniquely identifies the HPA to the controller. 
     Each host has an application resident thereon that provides topology information to the storage array controllers. At initiation of the network or whenever a change is sensed to the network, for example, a new device was added or a host port adapter was replaced, each host performs an identification process with every controller on the network. More particularly, each host discovers which controllers support the functionality of dynamically generating a topology of the network according to the invention. Each host then discovers all of the paths it has to access the controllers that support the topological functionality. Each host then sends a command preferably in the form of a fibre channel packet along every path it has coupling it to the controllers. The packet has a header, payload and trailer section. The header contains the world wide name of the host port adapter through which the command was sent. The payload contains information about the unique host identifier, cluster data, if applicable, as well as host type. The trailer section contains crc error information. By providing the information in this form, the host port adapter is linked with the host and cluster, if applicable so now it is known which host and cluster the host port adapter is associated with. The controller is also provided with information concerning what path was used to transmit the packet and what controller port received the packet. The controller keeps a table of this information which can be read out of the controller by the management console to dynamically generate the topology of the network as shown at  702  of FIG.  8 . Preferably, the management console has software resident thereon for using the information to generate a display of the topology on a screen of the management console. 
     If a change is made to the topology of the network such as a host port adapter is replaced or swapped, a command from the host application using the replaced adapter will supply all of the controllers with all of the information they need to modify topology accordingly. 
     FIG. 5 is a schematic diagram of a multiple cluster, single port controller, redundant path topology  500 . This topology may be used to share the storage array amongst two or more clusters. In this particular embodiment, server nodes  502 ,  506  are grouped into a first cluster  510  and server nodes  504 ,  508  are grouped into a second cluster  512 . Each cluster group is provided its own pair of ports to access the storage array  520 . The primary objective in this environment is to amortize the cost of the storage array across the multiple server cluster groups that are attached to the storage array, consolidate the management of the storage associated with the clustered servers attached to the storage array, provide the necessary LUN space environments for each of the clustered servers attached to the storage array, and provide simple cabling and integration for storage sharing of a multiple cluster group environment. 
     When configuring the storage partitions for multiple server clusters, the primary consideration is in providing the set of hosts in a cluster a single volume to LUN mapping. When configuring redundant controller configurations of the multiple cluster group configuration, it is required that the volume to LUN mappings are configured consistently for the multiple host adapter ports associated with that cluster group. This is to provide ease of management and also to support current operating system limitations and clustering applications with regard to LUN management. The cluster name is provided through a menu on the management console that provides the list of cluster names provided by the user. These cluster names represent collections of host adapters that have been configured by the administrator to be associated with the named clustered hosts. 
     As a clustered multiple port configuration example with reference to FIG. 5, assume that Cluster Group # 1  ( 510 ) wishes to have access to Volume ‘Bill’. To allow Cluster Group # 1  to access ‘Bill’ using the storage array ports connected to Cluster Group # 1 , the Logical Unit Number (LUN) to address ‘Bill’ should currently be the same for the host ports in the cluster group accessing the volume. Assuming Logical Unit Number=4 was chosen, the following entries would be required in the storage array controller storage partitioning volume to LUN Mapping Table: 
     
       
         
           
               
               
               
             
               
                   
               
               
                 Cluster Group 1 
                 Volume ID 
                 Nexus LUN ID 
               
               
                   
               
             
            
               
                 HPA #1 
                 Bill 
                 4 
               
               
                 HPA #2 
                 Bill 
                 4 
               
               
                 HPA #3 
                 Bill 
                 4 
               
               
                 HPA #4 
                 Bill 
                 4 
               
               
                   
               
            
           
         
       
     
     A user such as a system administrator is provided a pictorial representation of the SAN topology through the management console  222  (FIG. 3) and the user can dynamically assign volumes to hosts as needed. FIG. 7 illustrates a screen that may be displayed on the management console  222  to display the configured topology of the SAN to a system administrator. In this particular embodiment, five hosts  602 - 610  are operatively coupled to the storage subsystem  612  via two controllers  614 ,  616 , each controller having two controller ports. Additional hosts can be operatively coupled to the storage subsystem by using the “Add Host” Icon  618 . Volumes are then assigned to the host as needed preferably using a drag and drop type interface that prompts the user for parameters that are needed. 
     FIG. 8 is a display screen  700  that can be displayed at the management console. As can be seen in the left hand column of the primary window  704 , a list of hosts along with their ports is shown as well as any cluster information. It can be seen that clusters “ME” and “VJ” each have two hosts. Host “Mercury”, “Earth” and “Venus” each have one port whereas hosts “Jupiter” and “Mars” have two ports. The administrator can select a host or cluster by merely clicking on the host or cluster in the left window  702 . It can be seen from the screen displayed in FIG. 8 that the cluster “ME” has been selected. The administrator can then select from a menu bar what information or actions the administrator would like to access. As shown in the menu bar  706  of the display screen, the “Configure” menu  708  has been selected from the main menu. The “Configure” menu has two submenus, i.e. “topology” and “volume-to-LUN mapping.” If the administrator selects the topology submenu then a screen is displayed (not shown) from which the administrator can configure the topology of the network. For example, the administrator can change cluster groupings. The administrator can also assign volumes to clusters and hosts. In addition, the administrator can configure the volume to LUN mappings as was described in detail in U.S. Ser. No. 09/431,745 referred to above. 
     With the present invention, a user, such as a system administrator, can view all the logical and physical components of a storage array. The system administrator can view, monitor, configure and reconfigure the entire storage array. Access is provided to all storage partitions defined in the storage array, and monitoring includes all events associated with the storage array. This view is useful in environments in which the storage array is administrated by a central administrator for all the hosts or clusters configuring or monitoring the storage array. Alternatively, a system administrator may be provided with a view of only the logical and physical components associated with a particular host or group of hosts. From this view, the system administrator can view and monitor only the logical units and physical components that are defined to affect the performance, reliability, and availability of the storage defined to be a part of a particular storage partition definition. This view is useful in environments in which the storage array is administrated by multiple administrators; each administrator only having a view of the storage array as appropriate for the storage partition seen by that host or cluster. 
     To prevent accidental or malicious tampering with Volume to LUN mappings, a minimal security mechanism is required. Preferably, a password is required to enter a volume to LUN mapping. Another form of security that would be acceptable as a supplemental approach would be to provide a volume level password that would protect the volume to LUN mapping on a volume basis. 
     FIG. 9 is a block diagram of control logic according to a preferred embodiment used to access the SAN. This control logic is software that is run on the storage array controllers. It includes a low level driver  900 , a high level driver  902  and a RAID engine  904  which is a piece of software that performs RAID management. Raid engine  904  can be made up of several different elements including a microprocessor and dedicated logic. Stored within the high level driver  902  or source driver is a LUN-to-volume table  906 . The low level driver  900  receives I/O requests from a plurality of hosts. In this particular embodiment, inputs from SCSI hosts, Fiber Channel (FC) hosts and Ethernet hosts are received. The LUN-to-volume mapping table  906  is required within the source driver to allow commands issued for specified LUNs to be routed to the proper volume (physical storage unit) as seen by the RAID engine. 
     Advantageously, the present invention allows the high cost of highly available storage arrays to be spread across multiple server environments. In addition, because the cost is spread across multiple server environments, systems in the smaller, low cost server environments can have access to the much needed highly availability features of these storage arrays. 
     In addition, the administrator is allowed to define the partitions of storage such that each volume is accessible only to the hosts that the administrator has enabled them to be accessed. For instance, two different hosts servicing different departments such as the finance and the human resources departments may use the same storage subsystem without having access to one another&#39;s department data. 
     Finally, the topology of the network is automatically determined and conveyed to the administrator. 
     The above specification, examples and data provide a complete description of the manufacture and use of the composition of the invention. Since many embodiments of the invention can be made without departing from the spirit and scope of the invention, the invention resides in the claims hereafter appended.