Abstract:
A method, apparatus, article of manufacture, and system are presented for establishing redundant computer resources. According to one embodiment, in a system including a plurality of processor devices and a plurality of storage devices, the processor devices, the storage devices and the management server being connected via a network, the method comprises storing device information relating to the processor devices and the storage devices and topology information relating to topology of the network, identifying at least one primary computer resource, selecting at least one secondary computer resource suitable to serve as a redundant resource corresponding to the at least one primary computer resource based on the device information and the topology information, and assigning the at least one secondary computer resource as a redundant resource corresponding to the at least one primary computer resource.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    This application is a continuation application of U.S. Ser. No. 13/346,924, filed Jan. 10, 2012 which is a continuation application of U.S. patent application Ser. No. 12/955,053, filed Nov. 29, 2010, which is a continuation application of U.S. patent application Ser. No. 12/652,408, filed Jan. 5, 2010 (now U.S. Pat. No. 7,865,768), which is a continuation of U.S. patent application Ser. No. 11/904,061, filed Sep. 25, 2007 (now U.S. Pat. No. 7,661,019), which is a continuation of U.S. patent application Ser. No. 11/471,118, filed on Jun. 19, 2006 (now U.S. Pat. No. 7,290,167), which is a continuation of U.S. patent application Ser. No. 11/228,859, filed on Sep. 16, 2005 (now U.S. Pat. No. 7,191,358), which is a continuation of U.S. patent application Ser. No. 10/387,188, filed on Mar. 11, 2003 (abandoned), the entire disclosures of which are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    This invention is generally related to the field of clustering systems and remote mirroring technology. 
         [0003]    The use of clustering systems to accomplish fault-tolerance and/or load-balancing is becoming increasingly popular. Generally speaking, a clustering system may provide redundant resources so that if one portion of the system experiences failure, another portion can take over affected tasks or otherwise provide recovery from the failure. Also, a clustering system may use its redundant resources to process tasks in a more distributed manner, allowing different portions of the system to work inparallel in accomplishing tasks. 
         [0004]    A typical clustering system may be made up of two or more nodes, each having its own processing and storage capabilities. In one particular use of a clustering system, a primary node may comprise of a server and associated storage devices, while a secondary node may also comprise of another server and associated storage devices. The secondary node may be created to be similar to the primary node, in terms of processing, storage, and other capabilities. Here, the clustering system may maintain exact correspondence between the data storage of the primary node and the data storage of the secondary node, such that any write or read to data storage at the primary node is replicated at the secondary node. If the primary node fails as it performs its various tasks, the secondary node may take over the tasks performed by the primary node. For example, if a web server that is configured as a primary node in a clustering system fails for some reason, a secondary node may take over and serve web server functions in place of the failed primary node. A web site supported by such a system thus continues to operate with little or no down time. Web site visitors may continue to visit the associated web site as if no failure had occurred. In this example, providing a primary and a secondary node of similar capabilities allows the secondary node to be capable of taking over the tasks previously performed by the primary node. 
         [0005]    In other situations, the secondary node may have lesser capabilities than the primary node. For example, if the secondary node is only designed to temporarily take over the tasks of the primary node, or if the secondary node is only designed to record periodic snap shots of the data storage of the primary node, it may be sufficient to create the secondary node with lesser capabilities. This may be especially true if the cost associated with creating a similarly capable secondary node is to be avoided, or if failure of the primary node is not expected to extend beyond a certain amount of time. Thus, depending on the situation, the required capabilities of the secondary node may vary. 
         [0006]    The correspondence between the data storage of a primary node and the data storage of a secondary node storage may also be referred to as remote mirroring. This is especially the case if the data storage of the primary node is at a geographically distant location from the data storage of the secondary node. Remote mirroring may be carried out by different portions of a system. For example, in host-based remote mirroring, a host, such as a server, may be principally responsible for maintaining the correspondence between the data storage of the primary node and the data storage of the secondary node. In storage-based remote mirroring, a storage system, such as a storage area network (SAN), may be principally responsible for maintaining such correspondence. Depending on the implementation, remote mirroring may require separate software and equipment installation and/or configuration, in addition to that required by other parts of the clustering system. 
         [0007]    Currently, in order to realize the many advantages of a clustering system, the multiple nodes of a clustering system must be established by a system administrator. For example, in a clustering system having a primary and a secondary node, the system administrator must decide exactly what should be the processing, storage, and other capabilities of the secondary node, install or identify available resources meeting those capabilities, install required software, and perform necessary configurations to set up the clustering system. These steps involve factors that can be overwhelmingly complex and difficult to analyze for the system administrator, even if that person is an expert. Thus, the administrator may only be able to make a rough guess, in an ad hoc manner, as to what storage capability is needed for the secondary node. As discussed above, the required storage capability of the secondary node may vary from situation to situation, and it may not always be ideal to simply mimic the storage capability of the primary node. 
         [0008]    Furthermore, after the desired processing, storage, and other capabilities of the secondary node is decided, the administrator must go about looking for existing equipment in the system that fit the description, or install such equipment. In a large system having many different components, it may be extremely difficult and time-consuming for an administrator to search through all available resources in order to find the appropriate equipment. Finally, after the appropriate resources are decided and located, software installation and configuration may take additional time and effort. Thus, while clustering systems provide import fault-tolerance and/or load-balancing capabilities, the deployment of clustering systems remains largely a difficult and imprecise undertaking. 
       BRIEF SUMMARY OF THE INVENTION 
       [0009]    The present invention provides a method, apparatus, article of manufacture, and system for establishing redundant computer resources. According to one embodiment, in a system including a plurality of processor, a plurality of storage devices, and a management server connected via a network, the method comprises storing device information relating to the processor devices and the storage devices and topology information relating to topology of the network, identifying at least one primary computer resource, the at least one primary computer resource including at least one primary processor device and at least one portion of storage implemented in at least one primary storage device, selecting at least one secondary computer resource suitable to serve as a redundant resource corresponding to the at least one primary computer resource based on the device information and the topology information, the at least one secondary computer resource including at least one secondary processor device and at least one portion of storage implemented in at least one secondary storage device, and assigning the at least one secondary computer resource as a redundant resource corresponding to the at least one primary computer resource. 
         [0010]    If the at least one primary storage device has storage-based remote mirroring function, the at least one secondary computer resource may be selected such that the at least one secondary storage device also has storage-based remote mirroring function and is accessible from the at least one primary storage device. 
         [0011]    In one embodiment, the at least one secondary computer resource is selected based on at least one user-specified policy, which may include performance of the at least one secondary computer resource, reliability of the at least one secondary computer resource, and/or cost of the at least one secondary computer resource. 
         [0012]    In another embodiment, the step for selecting the at least one secondary computer resource comprises the steps of selecting at least one candidate suitable to serve as a redundant resource corresponding to the at least one primary computer resource, presenting the at least one candidate to a user, and receiving input from the user indicating selection, from the at least one candidate, of the at least one secondary computer resource. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a block diagram of a clustering system in accordance with at least one embodiment of the present invention. 
           [0014]      FIG. 2  is an illustration of a mapping table. 
           [0015]      FIG. 3  is an illustration of a logical unit number (LUN) binding table. 
           [0016]      FIG. 4A  is an illustration of a discovery list. 
           [0017]      FIG. 4B  is an illustration of a functional discovery list that may be maintained in addition to or in place of the discovery list shown in  FIG. 4A . 
           [0018]      FIG. 5  is an illustration of a topology table. 
           [0019]      FIG. 6A  illustrates a fibre channel switch (FC-SW) zoning configuration table. 
           [0020]      FIG. 6B  illustrates a different FC-SW zoning configuration table. 
           [0021]      FIG. 6C  illustrates a storage-based replication configuration table. 
           [0022]      FIG. 6D  illustrates a host-based replication configuration table. 
           [0023]      FIG. 6E  illustrates a cluster configuration table. 
           [0024]      FIG. 6F  illustrates a cluster resource group configuration table. 
           [0025]      FIG. 6G  illustrates a heartbeat configuration table. 
           [0026]      FIG. 7  is a flow chart summarizing the general steps involved in automatic configuration and semi-automatic configuration of a clustering system in accordance with at least one embodiment of the present invention. 
           [0027]      FIG. 8  depicts a visual configuration diagram that may be presented to the user. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Clustering System 
       [0028]      FIG. 1  is a block diagram of a clustering system  100  in accordance with at least one embodiment of the present invention. Here, clustering system  100  is comprised of equipment found in at least two geographically distinct locations  102  and  104 . For example, location  102  may be a metropolitan area such as San Diego, California, and location  104  may be a different metropolitan area such as San 
         [0029]    Francisco, California. At location  102 , a management server  106  is responsible for monitoring, configuring, and otherwise managing servers  108  and  110 , network equipment  112 , and storage equipment  113 ,  114 , and  115 . Management server  106 , servers  108  and  110 , network equipment  112 , and storage equipment  113 ,  114 , and  114  communicate through a local network  116 , forming a local SAN. 
         [0030]    As shown, management server  106  includes a SAN manager  118  that includes a configuration engine  120  and a topology repository  122 . SAN manager  118  also maintains a discovery list  124 , a configuration table  126 , a topology table  128 , and a mapping table  130 , which are discussed in further detail below. SAN manager  118  maintains this information by communicating with various management agents located in servers  108  and  110 , network equipment  112 , and storage equipment  113 ,  114 , and  115 . SAN manager  118  and the various management agents may be implemented in software. 
         [0031]    Server  108  may include one or more application programs. These application programs may be server level applications such as Web server applications, network file sharing applications, and others. As  FIG. 1  illustrates, server  108  may also include clustering software for maintaining a clustering system, a management agent, and a number of host ports. Server  110  is similarly arranged and may also include one or more application programs, clustering software, a management agent, and a number of host ports. 
         [0032]    Network equipment  112  is illustrated in  FIG. 1  as a switch having a number of switch ports. Network equipment  112  also includes a management agent. Network equipment  112  facilitates communication through local network  116 . As shown, network equipment  112  provides communication between servers  108  and  110  and storage equipment  115 . 
         [0033]    Storage equipment  115  may include a number of disk ports, a number of logical volumes  132 ,  134 , and  136 , and a management agent. Here, each of the logical volumes  132 ,  134 , and  136  may be implemented in different ways, such as by use of various types of redundant array of independent disks (RAID). Each of logical volumes  132 ,  134 ,  136  may be implemented on a single physical disk (not shown), across multiple physical disks (not shown) within a disk group (not shown), across disks in multiple disk groups, or in some other arrangement. 
         [0034]    Here, server  108 , network equipment  112 , and storage equipment  115  may represent a primary node in a clustering system. For example, server  108  may be executing a database application, using storage equipment  115  to store the associated databases and communicating data to and from storage equipment  115  through network equipment  112 . Fault-tolerance for this database service may be realized by creating a secondary node corresponding to the primary node. Use of equipment located at a geographically distinct location, such as location  104 , would provide effective fault-tolerance because if a catastrophic local event damages equipment at location  102 , redundant equipment at location  104  would be able to provide effective recovery. 
         [0035]    At location  104 , a management server  138  is responsible for monitoring, configuring, and otherwise managing a server  140 , network equipment  142 , and storage equipment  144 . Management server  138 , server  140 , network equipment  142 , and storage equipment  144  communicated through a local network  146 , forming a local SAN. Local SANs at locations  102  and  104 , and perhaps other local SANs, may together form a wide area SAN by communicating over one or more wide area networks  148 . 
         [0036]    As shown, management server  138  includes a SAN manager  150  that includes a configuration engine  152  and a topology repository  154 . SAN manager  150  also maintains a discovery list  156 , a configuration table  158 , a topology table  160 , and a mapping table  162 , which are discussed in further detail below. SAN manager  150  maintains this information by communicating with various management agents located in server  140 , network equipment  142 , and storage equipment  144 . SAN manager  150  and the various management agents may be implemented in software. 
         [0037]    Server  140  may include one or more application programs, clustering software for maintaining a clustering system, a management agent, and a number of host ports. Network equipment  142  is illustrated in  FIG. 1  as a switch having a number of switch ports. Network equipment  142  also includes a management agent. Network equipment  142  facilitates communication through local network  146 . As shown, network equipment  142  provides communication between server  140  and storage equipment  144 . 
         [0038]    Storage equipment  144  may include a number of disk ports, a pool  164  of logical volumes, from which logical volumes  166 ,  168 , and  170  may be selected, and a management agent. Here, each of the logical volumes in logical volume pool  164 , including logical volumes  166 ,  168 , and  170 , may be implemented in different ways, such as by use of various types of redundant array of independent disks (RAID). Thus, each of the logical volumes may be implemented on a single physical disk (not shown), across multiple physical disks (not shown) within a disk group (not shown), across disks in multiple disk groups, or in some other arrangement. 
         [0039]    Here, server  140 , network equipment  142 , and storage equipment  144  may be used to form a secondary node associated with the previously discussed primary node in the clustering system. For example, if the clustering system is designed to provide a secondary node having similar processing, storage, and other capabilities as those of the primary node, it would be desirable to identify a secondary node having similar equipment as the primary node. Server  140 , network equipment  142 , and storage equipment  144  may fit such requirements. The present invention allows equipment such as server  140 , network equipment  142 , and storage equipment  144  to be identified as resources that may be used to form the secondary node. 
         [0040]    Servers  108 ,  110 , and  140  are examples of processor devices, storage equipment  115  and  144  are examples of storage devices, and network equipment  112  and  142  are examples of network interface devices. 
       Information Maintained at Management Server and Elsewhere 
       [0041]      FIG. 2  is an illustration of mapping table  130  maintained in management server  106  of  FIG. 1 . Mapping table  130  is illustrated here as an example. Other mapping tables, such as mapping table  162  maintained in management server  138 , may have similar formats. As shown in  FIG. 2 , mapping table  130  provides a mapping between application programs being executed and the location(s) of data storage being utilized by such application programs. For instance, an application program executing in server  108  may utilize logical volumes  132 ,  134 , and  136  in storage equipment  115 , and mapping table  130  would register such utilization in detail. Different methods may be used to identify the various application programs executing in a particular server. One such method involves using the Common Information Model (CIM) standard, which allows application programs executing in a server may communicate with one another. For example, the management agent in server  108  may use the CIM standard to communicate with, and thereby identify, the various application programs executing in server  108 . Another method involves using repository information maintained by the operating system of the server. For example, the management agent in server  108  may retrieve data from the repository information of the operating system of server  108  to identify various application program executing in server  108 . 
         [0042]    Mapping table  130  is shown to include the following categories of information: ID  202 , Server  204 , Application  206 , Related Mount Point  208 , Related Volume ID  210 , Disk Group (DG) ID  212 , Block Device  214 , Logical Unit (LU) Binding ID  216 , Small Computer System Interface (SCSI) ID  218 , and SCSI Logical Unit Number (LUN)  220 . Here, table  130  indicates that a database (DB) application is executing in Server A (server  108 ). Table  130  further indicates that this DB application is utilizing logical volumes Vol 1 , Vol 2 , and Vol 3  (logical volumes  132 ,  134 , and  136 ). For each of these three logical volumes, table  130  provides additional information. Taking Vol 1  just as an example, table  130  indicates the mount point (/u01) at which Vol 1  is associated with, or “mounted” to, the system executing the DB application. Table  130  also indicates the physical disk group (0) and block device (c2t2d1) in which Vol 1  is implemented. In this example, logical volumes are also associated with SCSI IDs, as well as LUNs within particular SCSI IDs. Here, Vol 1  is shown to be associate with a particular SCSI ID (2) and a particular SCSI LUN (1). 
         [0043]      FIG. 3  is an illustration of a LUN binding table  300  maintained in server  108  of  FIG. 1 . LUN binding table  300  is illustrated here as an example. Other LUN binding tables maintained in other servers, such as servers  110  and  140 , may have similar formats. LUN binding table  300  indicates the SCSI ID assignment and LUN assignment associated with location(s) of data storage being utilized by application programs executing in server  108 . LUN binding table  300  is shown to include the following categories of information: Binding ID  302 , SCSI ID  304 , LUN  306 , and Inquiry Information  308 . Each Binding ID  302  indicates a particular location of storage and is associated with a particular SCSI ID  304  and a particular LUN  306 . Also, each Binding ID  302  further indicates Inquiry Information  308 , which can provide additional data such as vendor, storage type, and logical volume information. Binding table  300  may be maintained as a part of the operation of the management agent in server  108 . Thus, individual binding tables maintained at various servers, such as servers  108  and  110 , may be used to form the mapping table  130  shown in  FIG. 2 . 
         [0044]      FIG. 4A  is an illustration of discovery list  124  maintained in management server  106  of  FIG. 1 . Discovery list  124  is illustrated here as an example. Other discovery lists, such as discovery list  156  maintained in management server  138 , may have similar formats. As shown in  FIG. 4 , discovery list  124  provides a listing of devices available at various locations, such as locations  102  and  104 . Discovery list  124  shows the following categories of information for each device: Local SAN ID  402 , Discovery ID  404 , Device Type  406 , Device Information  408 , IP address  410 , and Area/Global Position  412 . Local SAN ID  402  identifies the local SAN to which the device belongs. Discovery ID  404  identifies a numerical order for the device within its local SAN. Device Information  408  may indicate various information relating to the device, such as vendor and device type. IP address  410  indicates the IP address assigned to the device. Area/Global Position  412  provides information relating to the location of the device, such as name of metropolitan area, longitude, and latitude. Thus, discovery list  124  allows management server  106  to identify available devices at various locations, including distant locations, that may be potential resources suitable to serve as part of a secondary node corresponding a primary node in a clustering system. 
         [0045]      FIG. 4B  is an illustration of a functional discovery list  440  that may be maintained in management server  106  of  FIG. 1 , in addition to or in place of discovery list  124 . Functional discovery list  440  is illustrated here as an example. Other discovery lists maintained in other management servers may have similar formats. As shown in  FIG. 4B , functional discovery list  440  provides a listing of devices available at various locations, such as locations  102  and  104 . Functional discovery list  440  shows the following categories of information for each device: Local SAN ID  442 , Discovery ID  444 , Function Type  446 , and Device Information  448 . Local SAN ID  442  identifies the local SAN to which the device belongs. Discovery ID  444  identifies a numerical order for the device within its local SAN. Function Type  446  provides information on the possible function of the device, such as use in host-based remote mirroring or storage-based remote mirroring. Device Information  448  may indicate various information relating to the device, such as vendor, device type, and device class. Functional discovery list  440  allows management server  106  to identify available devices at various locations, including distant locations, that may be potential resources suitable to serve as part of a secondary node corresponding a primary node in a clustering system. 
         [0046]      FIG. 5  is an illustration of topology table  128  maintained in management server  106  of  FIG. 1 . Topology table  128  is illustrated here as an example. Other topology tables, such as topology table  160  maintained in management server  138 , may have similar formats. As shown in  FIG. 5 , topology table  128  provides a summary of interconnections over which data may be sent in system  100 . Topology table  128  shows the following categories of information: server information  502 , first local network information  504 , interconnect information  506 , second local network information  508 , and storage information  510 . Topology table  128  depicts the manner by which various networking and storage equipment are linked, including local and wide area network connections. Here, topology table  128  is shown to be focused on storage network topology for purposes of illustration. Other types of topology information may be included as well. 
         [0047]      FIGS. 6A-6G  show various configuration tables that may be implemented, individually or in combination, as the contents of configuration table  126  maintained in management server  106  of  FIG. 1 . Contents of configuration table  126  is illustrated here as examples. Other configuration tables, such as configuration table  158  maintained in management server  138 , may have similar formats. 
         [0048]      FIG. 6A  illustrates a fibre channel switch (FC-SW) zoning configuration table  600 . This table contains categories of information including Zone ID  602  and Switch Port ID List  604 . Zone ID  602  identifies different zones, or groupings of devices, such that devices within a common zone may readily communicate with one another. Switch Port ID List  604  identifies the different network ports which belong to the identified zone.  FIG. 6B  illustrates a different FC-SW zoning configuration table  606 , similar in structure to table  600 . Zoning configuration tables  600  and  606  allow convenient separation of groups of devices. Here, tables  600  and  606  are described as fibre channel switch zoning configuration tables for purposes of illustration, other types of equipment may also be organized in similar zoning tables. 
         [0049]      FIG. 6C  illustrates a storage-based replication configuration table  608 . This table identifies the configuration of storage-based data replication from a set of primary storage locations to a corresponding set of secondary storage locations. Here, the storage system is responsible of maintaining the proper replication of data. Table  608  shows the following categories of information: ID  610 , Group ID  612 , Group Name  614 , primary storage information  616 , secondary storage information  618 , and Cluster Config ID  620 . ID  610  is an entry identifier. Group ID  612  and Group Name  614  relate to the identification number and name for each group of storage resources, such as a group of volumes, representing a storage location. The primary and secondary storage information  616  and  618  each identifies the host and volume information associated with the relevant storage location. Cluster Config ID  620  identifies a label for the cluster corresponding to the primary and secondary storage locations. 
         [0050]      FIG. 6D  illustrates a host-based replication configuration table  622 . This table identifies the configuration of host-based data replication from a set of primary storage locations to a corresponding set of secondary storage locations. Here, the host system is responsible of maintaining the proper replication of data. Table  622  shows the following categories of information: ID  624 , Valid  626 , Group ID  628 , Group Name  630 , primary storage location information  632 , secondary storage location information  634 , and Cluster Config ID  636 . Valid  626  relates to whether the particular replication configuration is available. Also, primary and secondary storage location information  632  and  634  are each shown to also include information for identifying the corresponding disk group and block device. Other information in table  622  is similar to information shown in table  608  of  FIG. 6C . 
         [0051]      FIG. 6E  illustrates a cluster configuration table  638 . This table identifies the arrangement of various clusters in the system, which may include the configuration of physical devices being controlled by cluster software. Table  638  shows the following categories of information: ID  640 , Valid  642 , Cluster ID/Name  644 , Cluster Type/Vender  646 , Member Node List  648 , Heartbeat List  650 , Heartbeat Configuration ID List  652 , Replication Type List  654 , and Replication Configuration ID List  656 . ID  640  identifies a numeric label for each entry, Valid  642  relates to whether the particular cluster is available. Cluster ID/Name  644  provides a number identifier and a name identifier for each cluster presented. Cluster Type/Vendor  646  identifies the classification of the cluster and vendor of the associated equipment. Member Node List  648  identifies the nodes that are members of the particular cluster. Heartbeat List  650  and Heartbeat Configuration  652  relate to arrangement of the heartbeat, which provides a signal that may be used to indicate whether a node, or particular resource at a node, is active. Replication Type List  654  and Replication Configuration ID List  656  relate to the type of replication available and the associated configuration label. 
         [0052]      FIG. 6F  illustrates a cluster resource group configuration table  658 . This table identifies the various resources available at different clusters, which may include the configuration of the logical resource group for each node in each cluster. Such resources may be processing, communication, storage, or other types of resources. Table  658  shows the following categories of information: ID  660 , Valid  662 , Cluster Type ID  664 , Resource Group ID  666 , Resource Group Name  668 , Member Node List  670 , Resource List  672 , Replication Type  674 , and Replication Configuration ID  676 . ID  660  provides an numerical label for each entry, Valid  662  relates to whether the particular cluster is available. Cluster Type ID  664  provides an identifier for the cluster and indicates the type and vendor of equipment associated with the cluster. Resource Group ID  666  and Resource Group Name  668  provide a number identifier and a name identifier for each collection of resources associated with the cluster. Resource List  672  identifies the particular resources available within the identified resource group. Replication Type  674  and Replication Config ID  676  relate to the type of replication available and the associated configuration label. 
         [0053]      FIG. 6G  illustrates a heartbeat configuration table  678 . This table identifies provides further detail on the arrangement of the heartbeat for each cluster. Table  678  shows the following categories of information: ID  680 , Valid  682 , Cluster 
         [0054]    Type ID  684 , Heartbeat Type ID  686 , Heartbeat Name  688 , Member Node List  690 , NIC List  692 , and Storage List  694 . ID  680  provides a numerical label for each entry. Valid  682  relates to whether the cluster is available. Cluster Type ID  684  provides an identifier for the cluster and indicates the type and vendor of equipment associated with the cluster. Heartbeat Type ID  686  and HeartBeat Name  688  identify the classification and name of the heartbeat utilized. For example, the heartbeat may be host-based or storage-based. Member Node List  690  identifies the nodes that are members of the particular cluster. NIC List  692  identifies NICs which correspond the to a particular host-base heartbeat. Storage list identifies storage systems which correspond to a particular storage-based heartbeat. 
         [0055]    The information maintained at each management server may be communicated to other management servers. For example, although management servers  106  and  108  are situated at geologically distinct locations  102  and  104 , respectively, they may exchange some or all of the information that is contained in various tables such as those discussed above. 
       Automatic Configuration 
       [0056]      FIG. 7  is a flow chart summarizing the general steps involved in automatic configuration and semi-automatic configuration of a clustering system in accordance with at least one embodiment of the present invention. The steps shown may be implemented as an integrated routine that allows the selection of either automatic configuration or semi-automatic configuration. Alternatively, the steps shown may be implemented as two separate routines. That is, a system may employ only automatic configuration, or only semi-automatic configuration. For purposes of illustration,  FIG. 7  shows the establishment of a clustering system through the formation of a secondary node corresponding to a primary node. Different steps shown in  FIG. 7  may be accomplished with use of a user interface, such as an interactive graphical user interface (GUI). Also, the GUI can be situated at any location, as long as the relevant information can be passed to the system. For example, the information submitted through the GUI by the user may be sent to the management server  106 , or to the management server  138 . 
         [0057]    Under automatic configuration, establishment of a clustering system begins with step  702 , in which the primary node of the planned clustering system is identified. This may involve identification, by the user, of the name of one or more target applications and the name of the target server corresponding to the primary node. Alternatively, a more automated process may be employed. For example, the main application executing in a target server may be selected. 
         [0058]    Next, in step  704 , policies for creating the clustering system, including remote mirroring features, may be specified. This step may involve specification by the user of general policies to follow in establishing the clustering system and importance assigned to such policies. For example, the user may be presented with three potential policies: (1) performance, (2) reliability, and (3) cost. 
         [0059]    Performance may relate to the effectiveness of the data transfer between the data storage of the primary node and the data storage of the secondary node, which may involve measures of bandwidth, distance, and network usage in a wide area SAN covering metropolitan areas of San Francisco (SF) and San Diego (SD) are provided in the table below: 
         [0000]    
       
         
               
               
               
             
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 Network 
                   
               
             
          
           
               
                   
                 Type 
                 Total 
                 Usage 
               
               
                   
                   
               
             
          
           
               
                   
                 SD 
                 Local 
                 2 Gbps 
                 50% 
               
               
                   
                 SF-SD 
                 Interconnect 
                 48 Gbps  
                 10% 
               
               
                   
                 SF 
                 Local 
                 2 Gbps 
                  8% 
               
               
                   
                   
               
             
          
         
       
     
         [0060]    Illustrative measures of bandwidth, distance, and network usage in the same wide area SAN, but from the perspective of the San Diego (SD) metropolitan area, are provided in the table below: 
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 Tested 
                   
                 Network 
               
             
          
           
               
                   
                 Type 
                 Throughput 
                 Distance 
                 Total 
                 Usage 
               
               
                   
                   
               
             
          
           
               
                 SF 
                 interconnect 
                 500 Mbps 
                 1000 mile 
                 48 Gbps 
                 10% 
               
               
                   
               
             
          
         
       
     
         [0061]    Thus, if a user places emphasis on performance, the secondary node may be chosen to have equal performance as the primary node, in terms of processing capability (server type), storage capability (throughput, cache size, RAID level, etc.), and network interface capability (number and performance of host bus adaptors). Also if there are two or more option for interconnects between the primary device and secondary device, the interconnect that has more available throughput capacity may be chosen. For example, assume there are two interconnects: interconnect A, which has 48 Gbps total throughput capacity and 10% average usage rate (43.2 Gbps available throughput capacity), and interconnect B, which has 128 Gbps total throughput capacity and 80% average usage rate (25.6 Gbps available throughput capacity). Here, interconnect A has more available throughput capacity than interconnect B, so interconnect A may be chosen. 
         [0062]    Reliability may relate to the level of confidence with which the data storage of the secondary node replicates data in the data storage of the primary node. If a user places emphasis on reliability the secondary node may be chosen to have redundant host bus adaptors and highly reliable, enterprise level storage, such as RAID level 1. Cost may relate to the cost of using equipment, such as maintenance costs. Cost may also relate to the cost of acquiring currently unavailable equipment. If a user places emphasis on cost, the secondary node may be chosen to have much lower performance than the primary node, in terms of processing capability (server type), storage capability (throughput, cache size, RAID level, etc.), and network interface capability (number and performance of host bus adaptors). For example, storage equipment of RAID level 5 may be chosen. 
         [0063]    Thus, by specifying general policies such as (1) performance, (2) reliability, and (3) cost, to follow in establishing the clustering system, the user is able control the design of the clustering system, without being required to decipher the detailed considerations relating to technical specifications of related equipment and software. The user may be presented with various general policies from which to choose. The user may specify policies by simply identifying particular policies as important. The user may also specify policies by assigning importance, or weight, to particular policies. This may be done in different ways, such as by user input of ratings, ratios, percentages, or other measures for different policies. 
         [0064]    The next step under automatic configuration is step  706 , in which information on the current system is gathered. Such information may include the contents of mapping tables, discovery tables, topology tables, and configuration tables. This information provides a detailed picture of the various aspects of the current system, including the mapping from applications to resources they utilize, available resource and their configurations, and so on. 
         [0065]    In step  708 , the information on the current system gathered in step  706  is analyzed to select the most appropriate resources and/or arrangements to be used for creating the secondary node. This is done in view of the various policies, and possibly weights assigned to those policies, as defined by the user in step  704 . In step  710 , the selected resources and/or arrangements are presented to the user, and the user is given to opportunity to confirm the selection of resources and/or arrangements. If the user confirms the selection, the process continues with step  712 , discussed below. If the user does not confirm the selection, the process loops back to step  704 . 
         [0066]    In step  712 , the selected resources and/or arrangements are used to create the secondary node. If the selected resources need additional software installation or configuration in order to function properly as the secondary node, such installation or configuration may be performed. Alternatively, the automatic configuration routine or semi-automatic configuration routine may re-select from resources that do not require additional software installation or configuration. Also, default resources that do not require additional software installation or configuration may also be selected in order to avoid such installation or configuration of software. Finally, in step  714 , the configuration table(s) are updated to include information on the secondary node just created. 
       Semi-Automatic Configuration 
       [0067]    Under semi-automatic configuration, establishment of a clustering system also begins with step  702 , which has been discussed previously. Next, in step  716 , information on the current system is gathered. This step is similar to step  706  discussed above. In step  718 , one or more potential selections of appropriate equipment and/or arrangements to be used for creating the secondary node is presented to the user. The user is given the opportunity to select the various equipment and/or arrangements to be used in creating the secondary node. In step  720 , the user&#39;s selection is received and presented back to the user for confirmation. Here, a visual topology diagram such as the one shown in  FIG. 8  may be presented to the user.  FIG. 8  may also represent a simplified version of block diagram shown in  FIG. 1  If the user confirms the selection, the process continues with step  712 , which is has been described previously. If the user does not confirm the selection, the process loops back to step  618 . 
         [0068]    In addition, semi-automatic configuration may also take into account user-defined policies, as is done in the case of automatic configuration. Here, such policies may allow potential selections of equipment and/or arrangements presented to be narrowed, so that the user may be presented with a more focused set of potential equipment and/or arrangements from which to make a selection. Other features discussed above in relation to automatic configuration may be adopted for use with semi-automatic configuration, and vise versa. For example, the visual confirmation diagram discussed in relation to semi-automatic configuration may also be used with automatic configuration, in order to present the automatically selected equipment and or arrangement to the user for confirmation. Further, variations on the different steps shown in  FIG. 7  may also be adopted. 
         [0069]      FIG. 1  is a block diagram of a clustering system  100  in accordance with at least one embodiment of the present invention. Such a diagram would allow the user to visually inspect a proposed configuration for a clustering system. This provides an efficient way to present a proposed configuration to the user for confirmation. 
         [0070]    Although the present invention has been described in terms of specific embodiments, it should be apparent to those skilled in the art that the scope of the present invention is not limited to the described specific embodiments. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense. It will, however, be evident that additions, subtractions, substitutions, and other modifications may be made without departing from the broader spirit and scope of the invention as set forth in the claims.