Abstract:
Provided is a method, system, program, and data structures for maintaining a database of objects. At least one structured document is received representing an instance of an object including attributes and attribute values defined for a class. Content of the structured document representing the object is added into a database, wherein the database is capable of storing multiple structured documents representing multiple objects. In another implementation, an instance of at least one object including attributes and attribute values defined for a class is generated. For each generated object, a structured document is generated representing the object and including a representation of the attributes and attribute values in the object. Each structured document is transferred to a database program to maintain.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a method, system, program, and data structures for testing a network system including input/output (I/O) devices. 
   2. Description of the Related Art 
   A storage area network (SAN) comprises a network linking one or more servers to one or more storage systems. Each storage system could comprise a Redundant Array of Independent Disks (RAID) array, tape backup, tape library, CD-ROM library, or JBOD (Just a Bunch of Disks) components. Storage area networks (SAN) typically use the Fibre Channel Arbitrated Loop (FC-AL) protocol, which uses optical fibers to connect devices and provide high bandwidth communication between the devices. In Fibre Channel terms the switch connecting the devices is called a “fabric”. The link is the two unidirectional fibers, which may comprise an optical wire, transmitting to opposite directions with their associated transmitter and receiver. Each fibre is attached to a transmitter of a port at one end and a receiver of another port at the other end. When a fabric is present in the configuration, the fibre may attach to a node port (N_Port) and to a port of the Fabric (F_Port). 
   Because a Fibre Channel storage area network (SAN) is an amalgamation of numerous hosts, workstations, and storage devices, troubleshooting for errors can often be a somewhat complex process. Currently, in the prior art, a technician will perform a series of tests from a host system in the SAN and test various channels and connections to the storage devices to detect problems and then try to locate the specific source of a problem. Technicians generally rely on their own knowledge, experience and expertise when diagnosing the SAN system for errors. Such knowledge is not a shared resource, but rather an individual point of view and an accumulation of guess work and personal experience. As a result, it is unlikely that different storage experts troubleshoot a storage system in the same manner, thereby leading to possible incorrect or inconsistent diagnosis as well as an increase in the Mean Time To Diagnose (MTTD). Moreover, as the number of SAN systems proliferate, it may become more and more difficult for system administrators to locate available diagnosticians. 
   Certain “cookbook” approaches to testing a Fibre Channel network have been proposed, such as the “Fibre Channel FC-AL-2 Parametric Test Suite Rev. 7.0”, published by the Fibre Channel Consortium, document no. ANSI X3.272-199X (January 2000), which publication is incorporated herein by reference in its entirety. Such documents describe specific tests that may be performed to troubleshoot a Fibre Channel network. However, again the order in which the tests are selected and performed is still a matter of choice for the diagnostician performing the troubleshooting operations. 
   Notwithstanding current efforts at troubleshooting network components, such as a SAN, the current art lacks tools that provide an integrated and consistent approach toward diagnostic testing of a SAN and its components. 
   SUMMARY OF THE DESCRIBED IMPLEMENTATIONS 
   Provided is a computer implemented method, system, and program for a diagnostic tool to automatically diagnose a system. A determination is made of a path in the storage system to test. The path includes path components including at least a host adaptor, a link, a device interface, and a device. A first test is performed to determine if there is a failure in the path. At least one of the path components is added to a suspect list capable of being a cause of the failure. The suspect list is implemented in a computer readable data structure. At least one isolation test is performed on at least one of the path components added to the suspect list. The tested path component is removed from the suspect list if the isolation test confirms that the tested path component cannot be a source of the failure. The suspect list is returned to a user to provide information on the path components capable of being the cause of the failure. 
   Further implementations concern a computer readable medium including data structures used to perform diagnostic testing of a system. A rule object includes code defining a flow of operations to perform diagnostic testing of a path in the system. The path includes path components including at least a host adaptor, a link, a device interface, and a device. The rule object calls test descriptors associated with a testing operation to perform. A test descriptor object includes test descriptors. Each test descriptor specifies one or more program modules to perform the testing operation associated with the test descriptor. A module object includes program modules providing code to perform testing operations. A call to one test descriptor executes the program modules specified by the test descriptor to perform diagnostic testing operations according to the operation flow specified in the rule object. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Referring now to the drawings in which like reference numbers represent corresponding parts throughout: 
       FIG. 1  illustrates a network computing environment in which preferred embodiments may be implemented; 
       FIG. 2  illustrates an implementation of an expert diagnostic software tool in accordance with certain implementations of the invention; and 
       FIGS. 3-13  illustrate logic implemented in the expert diagnostic tool to perform diagnostic testing of a storage system in accordance with certain implementations of the invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   In the following description, reference is made to the accompanying drawings which form a part hereof and which illustrate several embodiments of the present invention. It is understood that other embodiments may be utilized and structural and operational changes may be made without departing from the scope of the present invention. 
     FIG. 1  illustrates an example of a storage area network (SAN) topology utilizing Fibre Channel protocols which may be tested using the expert diagnostic tool of the described implementations. Host computers  2  and  4  may comprise any computer system that is capable of submitting an Input/Output (I/O) request, such as a workstation, desktop computer, server, mainframe, laptop computer, handheld computer, telephony device, etc. The host computers  2  and  4  would submit I/O requests to storage devices  6  and  8 . The storage devices  6  and  8  may comprise any storage device known in the art, such as a JBOD (just a bunch of disks), a RAID array, tape library, storage subsystem, etc. Fabric  10  comprises a switch connecting the attached devices  2 ,  4 , and  8 . In the described implementations, the links  12   a, b, c, d, e, f  connect the devices comprise Fibre Channel Arbitrated Loops or fiber wires. In alternative implementations, the different components of the system may comprise any network communication technology known in the art. Each device  2 ,  4 ,  6 , and  8  includes multiple Fibre Channel interfaces  14   a ,  14   b ,  16   a ,  16   b ,  18   a ,  18   b ,  20   a ,  20   b ,  22   a , and  22   b , also referred to as a port, device or host bus adaptor (HBA), and a Gigabyte Interface Converter Modules (GBIC)  24   a-l.  The GBICs  24   a-l  convert optical signals to electrical signals. The fibers  12   a, b, c, d, e, f;  interfaces  14   a, b,    16   a, b,    18   a, b,    20   a, b,    22   a, b,  and GBICs  24   a-l  comprise individually replaceable components, or field replaceable units (FRUs). The components of the storage area network (SAN) described above would also include additional FRUs. For instance, the storage devices  6  and  8  may include hot-swapable disk drives, controllers, and power/cooling units, or any other replaceable components. For instance, the Sun Microsystems&#39; Ax5000 storage array has an optical interface and includes a GBIC to convert the optical signals to electrical signals that can be processed by the storage array controller. The Sun Microsystems&#39; T 3  storage arrays includes an electrical interface and includes a media interface adaptor (MIA) to convert electrical signals to optical signals to transfer over the fiber. 
   A path, as that term is used herein, refers to all the components providing a connection from a host to a storage device. For instance, a path may comprise host adaptor  14   a,  fiber  12   a,  initiator port  22   a,  device port  22   c,  fiber  12   e,  device interface  20   a,  and the storage devices or disks being accessed. The path may also comprise a direct connection, such as the case with the path from host adaptor  14   b  through fiber  12   b  to interface  16   a.    
     FIG. 2  illustrates an implementation of the architecture of a storage diagnostic tool  100  that may be installed on host systems  2  and  4  to test the paths to the storage devices  6  and  8  through the fabric  10  or directly connected to the storage device, e.g., fiber links  12   b, f.  The expert diagnostic tool  100  includes a state machine  102  that is the program component including code to manage and execute rules from the rule base  104 . The rule base  104  code defines the general flow of the diagnostic operations. The rule base code references test descriptors within the test descriptions module  106 . Each test description included in the test descriptions module  106  references one or more of the routines from the test modules  108 , which in turn may reference one or more library modules  110  that perform basic operations shared by different test modules. Each test module includes code implementing a particular test operation. As the state machine  102  is executing the testing modules, the state machine  102  would add field replaceable units (FRU) within the storage area network (SAN) paths being tested that could be the source of any detected errors to a suspect list  112  file. If during testing operations, the rule base  104  determines that a FRU previously placed on the suspect list  112  is replaced or otherwise determined to not be the source of the failure or error, then the FRU would be removed from the suspect list  112 . 
   The state machine  102  would begin performing the testing routine outlined in the rule base  104  in response to user input commands invoking the expert diagnostic tool  100  entered through a host system  2 ,  4  interface, such as a command line or graphical user interface (GUI). The rule base  104  implements a testing routine an expert would perform including determinations an expert diagnostician would make based on the outcome of certain of the tests.  FIGS. 3-13  illustrate the logic flow of the code included in the rule base  104 , which calls the test descriptions  106 , where each test description would specify one or more of the test modules  108  to execute to carry out the test specified by the test description. 
     FIGS. 3-13  illustrate logic implemented in the rule base  104  to automatically and consistently perform an expert system diagnosis of the SAN shown in FIG.  1 . Following are some of the test descriptors used in the logic of  FIGS. 3-13  to implement the expert diagnostic system. Each test descriptor would be comprised of one or more of the test modules  110 , which themselves may be comprised of one or more library modules:
         STRESS TEST: specifies various testing algorithms to determine if the path between the host bus adaptor (HBA)  14   a, b    18   a, b  and storage device  6 ,  8  is working properly.   IS DISK: determines a type of the storage device  6 ,  8 , e.g., a Sun StorEdge A5200 disk array or T 3  array, etc.** The disk type may specify whether the disk is addressed directly, such as the case with a JBOD, or logically addressed through a volume manager. There may be different IS_DISK test descriptors that are checked for each disk type that may be included in the SAN.   IS SWITCHED: Determines whether a switch is located between the hosts  2 ,  4  and storage device  6 ,  8 , e.g., fabric  10 , or whether there is a direct connection, e.g., fiber  12   b, f.      DPORT TEST: Specifies one or more diagnostic tests to determine whether the connection  12   d, e  between the device ports  22   c, d  and storage device  8  interface  20   a, b  is functioning properly.   REM DPORT FIBER: Instructs the administrator through a user interface to remove the fiber connection to the device port  22   c, d,  i.e., disconnect or unplug the fiber from the port.   INS DPORT LB: Instructs the administrator to install the loopback fiber on the GBIC  24   i, j  at the device port  22   c, d  to allow reading and writing through the loopback path of the port. During loopback diagnostics, data sent through the loopback path is compared with the originally sent data to determine if the data has changed during transmission through the loopback. The diagnostic tests may also perform statistical analysis of the data to detect any anomalies.   REM DPORT LB: Instructs the administrator to remove loopback fiber to allow the device port  22   c, d  to communicate over the fiber  12   d, e.      REP DPORT FIBER: Instructs the administrator to replace the fiber  12   d, e  between the device port  22   c, d  and the storage device  8  to isolate the fiber.   REST DPORT FIBER: Instructs the administrator to reinstall the fiber that was previously replaced to isolate test the device port fiber  12   d, e.      REP DEV: Instructs the administrator to remove current storage device FRUs, e.g., the GBIC  24 ,  k, l,  and replace with new device FRUs to perform isolation testing on the storage device components. For instance, the device FRUs may comprise the GBICs  24   k, l,  or if the storage device  8  is a Sun StorEdge T 3  array, the FRU may comprise a media interface adaptor (MIA).   REST DEV: Instructs the administrator to reinstall the device interface FRUs, e.g., the GBIC  24 ,  k, l,  previously removed in response to the REP_DEV descriptor.   IS DISK AVAILABLE: Determines whether a disk is online and available. There may be different IS_DISK_AVAILABLE descriptors for each different type of device determined by the IS_DISK descriptor.   DISK ISOLATION: Provides algorithms to perform series of test to determine if disks in the storage device  6 ,  8  are functioning properly.   REP DPORT GBIC: Instructs the administrator to replace the device port GBIC  24   i, j  to isolate the fiber device port.   IPORT TEST: Specifies one or more diagnostic tests to run to determine whether the path  12   a, c  between one initiator port  22   a, b  and one host adaptor  14   a,    18   a  is functioning properly.   IS HBA: determines a type of the host adaptor  14   a, b,    18   a, b,  e.g., a Fibre Channel arbitrated loop adaptor, e.g., the StorEdge PCI FC-100 adaptor, the S-bus FC100 HA adaptor, etc. There may be multiple IS_HBA test descriptors that are checked for the different types of host adaptors included in the SAN.   LBF TEST: Specifies one or more diagnostic tests to perform a loopback frame test on an adaptor or interface to determine whether the data transmitted is not erroneously altered during transmission through the data path component.   REM IPORT FIBER: Instructs the administrator through a user interface to disconnect the fiber connection to the initiator port  22   a, b,  i.e., unplug the fiber from the port.   REP IPORT FIBER: Instructs the administrator to replace the fiber  12   a, c  between the host  2 ,  4  and the fabric  10 .   REST IPORT FIBER: Instructs the administrator to reinstall the fiber that was previously replaced to isolate test the initiator port fiber  12   a, c.      REM HBA FIBER: Instructs the administrator through a user interface to disconnect the fiber connection  12   a, b, c, f,    18   a  at the host adaptor  14   a, b,    18   a, b,  i.e., unplug the fiber from the host adaptor port.   HBA TEST: Specifies one or more diagnostic tests to run to determine whether the host adaptor  14   a, b,    18   a, b  is functioning properly. There may be separate HBA_TESTs for different host adaptor types, determined using the IS_HBA descriptor.   INS HBA LB: Instructs the administrator to insert the loopback fiber at the host adaptor to allow for loopback testing of a GBIC  24   a, b, e, f  of the host adaptor. Thus, after the fiber  12   a, b, c, f  is removed from the host adaptor  14   a, b,    18   a, b  the loopback fiber that provides a loopback path is inserted at the host adaptor to allow for loopback testing.   HBA GBIC TEST: Specifies one or more loopback diagnostic tests to perform to determine whether the host adaptor GBIC  24   a, b, e, f  is functioning properly.   REST HBA FIBER: Instructs the administrator to reinstall the fiber that was previously removed from the host adaptor.   REP HBA GBIC: Instructs the administrator to replace the host adaptor GBIC  24   a, b, e, f  to isolate the host adaptor GBIC.       
   The diagnostic routine begins at block  200  in FIG.  3 . The state machine  102  calls (at block  202 ) the STRESS_TEST test descriptor to test the integrity of the path from the host bus adaptor (HBA)  14   a,    14   b,    18   a,    18   b  to an interface  16   a, b,    20   a, b  in the storage device  6 ,  8 . The administrator may specify a path from the host to one of the storage devices, including the host adaptors and device interfaces on the path. If the STRESS_TEST fails, then the state machine  102  calls the IS_DISK descriptor to determine the target disk type. The determined disk type is added (at block  208 ) to the suspect list  112 , e.g., indicating a disk or LUN as the suspect. The state machine  102  then calls the IS_SWITCHED test descriptor if (at block  210 ) the loop or connection between the host  2 ,  4  and storage device  6 ,  8  includes a switch, e.g., fabric  10 . If there is a switch, then the DPORT_TEST test descriptor is called (at block  212 ) to test the loop between the device port (DPORT)  22   c,    22   d  and the storage device interface  20   a, b.    
   If (at block  214 ) the device port connection  12   d, e  is not operating properly according to the DPORT_TEST, then all the components on the connection between the fabric  10  and storage device  8  are added (at block  216 ) to the suspect list as possible sources of the failure, including any field replaceable units (FRUs) for the device port  22   c, d  and interface  20   a, b,  which may include GBICs  24   i, j, k, l,  the switch  10 , and the fiber  12   d, e.  The IS_DISK descriptor is called (at block  218 ) to determine the target disk type on the connection being checked, so that any field replaceable units (FRUs) within the storage device  8  may be added (at block  220 ) to the suspect list  112 , e.g., the GBIC  24   k, l.  The state machine  102  then calls (at block  222 ) the REM_DPORT_FIBER to disable the connection, i.e., disconnect, from the device port  22   c, d  to the fiber  12   d, e  and then calls INS_DPORT_LB to enable the loopback feature on the device port  22   c, d.  If (at block  224 ) the administrator (referred to as “admin” in the figures) acknowledges that the manual operations requested at block  222  were not performed, then the diagnosis ends (at block  226 ) and the suspect list  112  is returned with all the components added, which at block  226  includes all the suspect components between the device port  22   c, d  and storage device  8 . If the administrator indicates through a user interface that the requested manual operation was performed, then control proceeds to block  228 . Note that whenever the state machine  102  requests the administrator to perform a manual operation, the diagnostic test would end, as at block  226 , if the administrator indicates that the requested manual operation was not performed. The manual operations involve the administrator replacing parts or disconnecting components to allow isolation testing of specific components. The diagnostic expert program continues if the administrator indicates that the requested manual operation was performed. 
   At block  228 , the state machine  102  calls the DPORT_TEST descriptor to isolate the device port  22   c, d  now that it is not connected on the fiber  12   d, e.  To communicate with the fabric  10 , the hosts  2 ,  4  and fabric  10  would include an Ethernet or other network adaptor to allow for out-of-band communication outside of the fiber connection. In this way, the hosts  2 ,  4  can communicate with the fabric  10  when the fiber  12   a, c  are unplugged. Out-of-band communication is used whenever the hosts  2 ,  4  need to communicate with a SAN component where the fiber link has been disconnected. If(at block  230 ) the device port passed, then control proceeds (at block  232 ) to block  250  in  FIG. 4  to proceed to test components downstream of the device port  22   c, d  as the isolated device port was confirmed as operational. With respect to  FIG. 4 , at block  250 , the state machine  102  removes (at block  250 ) the switch and the device port GBIC  24   i, j  from the suspect list  112 . The REM_DPORT_LB descriptor is called (at block  252 ) to instruct the administrator to remove the loopback connection and REP_DPORT_FIBER is called to instruct the administrator to replace the fiber wire  12   d, e  with a new fiber to allow isolation testing of the device port fiber  12   d, e.  The state machine  102  calls (at block  258 ) the DPORT_TEST descriptor to test whether replacing the fiber corrected the problem. If (at block  260 ) the test succeeded, then the state machine  102  calls (at block  262 ) the IS_DISK test descriptor to determine the disk type, and remove the disk and any disk FRUs, e.g., the disk GBICs  24   k, l,  from the suspect list  112 . Control proceeds to block  264  to prompt the administrator to retry the test from the start at block  200  in  FIG. 3  to test the SAN with the new fiber  12   d, e.    
   If (at block  260 ) the test with the new fiber did not succeed, then the state machine  102  removes (at block  266 ) the device port fiber  12   d, e  from the suspect list  112 . The REST_DPORT_FIBER descriptor is called (at block  268 ) to instruct the administrator to reinstall the previously removed fiber link because the replaced fiber was not one cause of the failure. IS_DISK is called (at block  270 ) to determine the disk type. The state machine  102  then calls (at block  272 ) the REP_DEV descriptor to instruct the administrator to replace FRUs, e.g., GBIC, MIA, etc., in the storage device interface  20   a, b.  The DPORT_TEST descriptor is called (at block  274 ) to isolate test the device interface. If (at block  276 ) the test succeeds, then the state machine  102  calls (at block  278 ) the IS_DISK descriptor to determine the disk type to remove the disk FRUs from the suspect list  112 . Control then proceeds to block  264  to prompt the administrator to retry the test with the new disk components. If the test did not succeed, i.e., the disk interface FRUs were not the source of the problem, then control proceeds (at block  280 ) to block  300  in  FIG. 5  to isolate the storage device  8 . 
   With respect to  FIG. 5 , to isolate the storage device, such as the disks in the storage device, the state machine  102  calls (at block  300 ) the IS_DISK descriptor to determine the disk type, and remove the disk interface  20   a, b  FRUs, e.g., GBIC  24   k, l,  from the suspect list  112 . The REST_DEV descriptor is called (at block  302 ) to instruct the administrator to reinstall the previously removed device interface  20   a, b  FRUs, as these were not the source of the failure. The state machine  102  then calls (at block  304 ) IS_DISK to determine the disk type, and then calls IS_DISK_AVAILABLE to determine whether the determined disk type is installed and online. If (at block  306 ) the disk is not available, then the state machine adds (at block  308 ) information to the suspect list  112  indicating that the disk is not available, e.g., not installed nor online. The diagnosis then ends (at block  310 ) and reports the possible failing components on the suspect list  112 , which from block  308  includes the disk. If the disk is available, then the state machine  102  calls (at block  314 ) the DISK_ISOLATION descriptor to run a series of isolation tests on the disk. If (at block  316 ) the disk passes the tests, then the disk type is removed (at block  318 ) from the suspect list  112  and the routine ends. Otherwise, if the disk does not pass the tests, then the test routine ends with the disk of the test storage device  8  on the suspect list  112 . Note that because the isolation of the disks was performed after a newly added device interface  20   a, b  FRUs was added, if at block  316  the disk passes the test, then the entire SAN is tested and operational with the new device FRUs. If the diagnostic test is performed from the beginning with the new component, then the suspect list  112  includes the replaced component to remind the administrator that a suspect component was removed. 
   With reference to  FIG. 3 , if (at block  230 ), the isolated device port  22   c, d  did not pass the tests, then control proceeds (at block  234 ) to block  350  in  FIG. 6  to further isolate components at the device port. With respect to  FIG. 6 , the state machine  102  calls (at block  350 ) the REP_DPORT_GBIC descriptor to instruct the administrator to replace the device port GBIC  24   i, j  and calls INS_DPORT_LB to instruct the administrator to install the loopback connection for loopback testing of the device port GBIC  24   i, j.  The descriptor DPORT_TEST is called (at block  352 ) to perform the diagnostic test on the device port  22   c, d  with the new GBIC. If (at block  354 ) the test succeeds, then the replaced device port GBIC can be assumed to have been one source of the failure, and the state machine  102  calls (at block  356 ) IS_DISK to determine the disk type and remove from the suspect list  112  the FRUs for the determined disk type, e.g., GBIC  24   k, l,  the disk type, the fiber link, and the switch. The descriptor REST_DPORT_FIBER is called (at block  358 ) to instruct the administrator to replace the loopback connection with the previously removed fiber link, which was not the source of the error. The state machine  102  then prompts (at block  360 ) the administrator to retry the diagnostic test with the new device port GBIC  24   i, j.  If (at block  354 ) the test with the new device port GBIC did not pass, then the replaced device port GBIC  24   i, j  could not have been the sole source of the error. In such case, the state machine  102  calls the IS_DISK descriptor (at block  362 ) to determine the disk type, and removes the determined disk type, FRUs for the determined disk type, the fiber link, and the device port GBIC  24   i, j  from the suspect list  112 . The REST_DPORT_FIBER descriptor is called (at block  364 ) to instruct the administrator to replace the previously removed fiber link  12   e, d.  At this point, the test ends (at block  366 ) with the switch, i.e., fabric  10 , remaining on the suspect list  112 . 
   If (at block  214 ) the switched path from the device port  22   c, d  to the storage device  8  did pass the DPORT_TEST, then control proceeds (at block  213 ) to block  380  in  FIG. 7  to test the path from the initiator port  22   a, b  in the fabric  10  to the host bus adaptor (HBA)  14   a,    18   a.  With respect to  FIG. 7 , the state machine  102  calls (at block  380 ) the IPORT_TEST descriptor to determine whether the path between one host adaptor  14   a,    18   a  and the initiator port  22   a, b  in the fabric  10  is functioning properly. If (at block  382 ) the path passes the tests, then the IS_HBA descriptor is called (at block  384 ) to determine the host adaptor type. 
   If (at block  386 ) the determined host adaptor type is one that does not support loopback frame testing, then the state machine  102  proceeds (at block  388 ) to block  304  in  FIG. 5  to isolate the storage device  8  because the initiator port  22   a, b  passed the test. Otherwise, if loopback frame testing is supported, the LBF_TEST descriptor is called (at block  390 ) to run a loopback frame test at the host adaptor  14   a,    18   a.  If (at block  392 ) the loopback test passed, then the host adaptor  14   a,    18   a  proceeds (at block  388 ) to block  304  in  FIG. 5  to isolate the storage device  8 . If the test of the path from the host  2 ,  4  to the fabric  10  failed at blocks  382  or  392 , then the state machine  102  calls (at block  394 ) IS_DISK to determine the disk type and removes the determined disk type from the suspect list because the fault likely lies in the path between the host adaptor  14   a,    14   b  and the initiator port  22   a, b.  Accordingly, also added (at block  396 ) to the suspect list  112  are the FRUs for the initiator port, e.g., the GBICs  24   g, h,  the fiber  12   a, c,  the host adaptors  14   a,    18   a,  any host adaptor FRUs, e.g., GBICs  24   a,    24   e,  and the switch  10 . 
   To begin fault isolation of the path between the host  2 ,  4  and the fabric  10 , the state machine  102  calls (at block  398 ) the REM_IPORT_FIBER to instruct the administrator to remove the link and install the loopback connection for loopback testing at the initiator port  22   a, b.  The IPORT_TEST descriptor is called (at block  400 ). If (at block  402 ) the test passes, then the error must be in the fiber  12   a, c  or the host adaptor  14   a,    18   a,  and the state machine  102  removes (at block  404 ) the initiator port  22   a, b,  any initiator port FRUs, e.g., the GBICs  24   g, h,  the fabric  10  or switch. The state machine  102  then calls (at block  406 ) the REP_IPORT_FIBER descriptor to instruct the administrator to replace the fiber  12   a, c  connecting the host  2 ,  4  to the fabric  10 . The IPORT_TEST descriptor is then called (at block  408 ) to test the new fiber. If (at block  410 ) the test passed, then the IS_HBA descriptor is called (at block  412 ) to determine the host adaptor type. Control proceeds (at block  414 ) to block  450  in  FIG. 8  to perform additional testing of the host adaptor if (at block  450 ) loopback frame testing is enabled in the host adaptor type. If so, then the LBF_TEST is called (at block  452 ) to run a loopback frame test at the host adaptor  14   a,    18   a  . If the loopback frame test passes or the loopback connection is not installed at the host adaptor  14   a,  b, then the error is assumed to be in the fiber  12   a, c.  In such case, the state machine  102  calls (at block  456 ) IS_HBA to determine the host adaptor type and remove the host adaptor and any host adaptor FRUs from the suspect list. The user is then prompted (at block  458 ) to retry the diagnostic test with the new fiber between the host  2 ,  4  and the fabric  10 . 
   If the loopback frame test did not pass at block  454  or the IPORT_TEST at block  410  on the new fiber did not pass, then the error is not in the fiber because replacing the fiber did not eliminate the failure. In such case, the state machine  102  calls (at block  460 ) REST_IPORT_FIBER to prompt the administrator to replace the fiber with the previously removed fiber and removes (at block  462 ) the initiator port fiber  12   a, c  from the suspect list  112 . The state machine  102  then calls (at block  464 ) the REM_HBA_FIBER descriptor to remove the connection of the host bus adaptor  14   a,    18   a  to the fiber  12   a, c  to isolate test the host adaptor  14   a,    18   a.  The IS_HBA descriptor is called (at block  466 ) to determine the host adaptor type, which is then used to determine the appropriate HBA_TEST descriptor to call to test the host adaptor  14   a,    18   a,  which is called (at block  466 ) to test the host adaptor  14   a,    18   a.  If (at block  468 ) the host adaptor  14   a,    18   a  fails the test, then the host adaptor  14   a,    18   b  is the cause of the failure. In such case, the host adaptor FRUs, e.g., the host adaptor GBICs  24   a, e,  are removed (at block  467 ) from the suspect list  112 . The test then ends (at block  472 ) with the host adaptor remaining on the suspect list  112 . Otherwise, if the host adaptor passed the test, then the host adaptor  14   a,    18   a  is not the cause of the failure and control transfers to block  474  to remove the host adaptor from the suspect list  112 . If (at block  476 ) the host adaptor type includes a replaceable GBIC, then the state machine  102  calls (at block  480 ) the INS_HBA_LB descriptor to instruct the administrator to install the loopback connection to allow loopback testing. 
   The state machine  102  then calls (at block  480 ) the HBA_GBIC_TEST descriptor to test the host adaptor GBIC  24   a, e.  If (at block  482 ) the test passes, then all components have passed the test. In such case, the REST_HBA_FIBER descriptor is called (at block  484 ) to reconnect the host adaptor  14   a,    18   a  to the fiber  12   a, c  and the remaining components, e.g., the host adaptor GBIC, are removed (at block  486 ) from the suspect list  112 . At this point, the administrator would be prompted to retry the test as the error may be of an intermittent nature and not detected during the previous diagnostic test. 
   If (at block  482 ) the host adaptor GBIC  14   a,    18   a  did not pass the test, then control proceeds (at block  490 ) to block  500  in  FIG. 9  to replace and retest the host adaptor GBIC with a new component. With respect to  FIG. 9 , at block  500 , the state machine  102  calls the REP_HBA_GBIC descriptor to instruct the administrator to replace the host adaptor GBIC  24   a, e  with a new unit and calls INS_HBA_LB to install the loopback for loopback testing of the new GBIC. The state machine  102  then calls (at block  502 ) the TEST_HBA_LOOP to loopback test the new host adaptor GBIC. If (at block  504 ) the test passes, then the host adaptor GBIC can be assumed to be one source of the failure. In such case, the state machine  102  calls (at block  506 ) the REST_HBA_FIBER descriptor to instruct the administrator to reconnect the fiber  12   a, c  to the host adaptor  14   a,    18   a.  The administrator is further prompted (at block  508 ) to retest the SAN with the new host adaptor GBIC to determine if any additional components are the source of the error. If (at block  504 ) the test of the new host adaptor GBIC did not pass, then all the components have been tested, and the error may be intermittent. In such case, the REST_HBA_FIBER is called (at block  512 ) to prompt the administrator to reconnect the fiber  12   a, c  to the host adaptor  14   a,    18   a  and the administrator is prompted (at block  514 ) to retry the diagnostic test again. If (at block  476 ) the host adaptor does not have a GBIC, then control proceeds (at block  492 ) to block  512  in  FIG. 9  to prompt the user to retry the test at block  514 . 
   If (at block  410 ) the new fiber did not pass the fiber isolation test, then control proceeds (at block  416 ) to block  460  in  FIG. 8  to reinstall the previously removed fiber and continue testing as the fiber is not the sole source of the failure. 
   If (at block  402 ) the isolated initiator port  22   a, b  does not pass the IPORT_TEST, then control proceeds (at block  418 ) to block  550  in  FIG. 10  to further test the initiator port  22   a, b  to pinpoint the source of the failure. With respect to  FIG. 10 , at block  550 , the state machine  102  calls the REM_IPORT_LB, REP_IPORT_GBIC, and INS_IPORT_LB, which are similar to REM_DPORT_LB, REP_DPORT_GBIC, and INS_DPORT_LB except performed with respect to the initiator port  22   a, b  as opposed to the device port  22   c, d.  These test descriptors are called to instruct the administrator to replace the initiator port GBIC  24   g, h  to allow for isolation of the initiator port  22   a, b  FRUs. The IPORT_TEST descriptor is then called (at block  552 ) to test the new initiator port GBIC. If (at block  554 ) the new GBIC passes the test, then the initiator port GBIC may be assumed to be one source of failure. In such case, the state machine  102  removes the initiator port fiber, fabric  10 , e.g., switch, and any host adaptor FRUs, e.g., GBIC  24   a, b  from the suspect list  112 . The state machine then calls descriptors (at block  558 ) to reconnect the initiator port  22   a, b  to the fiber  12   a, c  and prompt (at block  560 ) the administrator to retry the test with the new GBIC. If the new initiator port GBIC did not pass the test, then the initiator port fiber  12   a, c,  initiator GBIC  24   g, h,  and any host adaptor FRUs are removed from the suspect list  112 . At block  564 , the state machine  102  calls descriptors to instruct the administrator to reinstall the previously removed GBIC. At block  566 , the test ends with the fabric  10 , i.e., switch, on the suspect list  112 . 
   If (at block  210 ) the loop is not switched, i.e., a direct connection for the host  2 ,  4  and the storage device  6  as shown on paths using fibers  12   b, f,  then a series of diagnostic tests are performed, as described with respect to  FIGS. 11 and 12  to isolate the host adaptor  14   b,    18   b,  fiber  12   b, f  or storage device interface  16   a, b  components in a manner similar to that described above, except there are no fabric  10  components to test, such as the initiator and device ports and their GBIC. 
     FIG. 13  illustrates test logic performed if at block  204  the SAN passes the initial STRESS_TEST.  FIG. 13  performs additional isolation testing of the components even if the SAN passes the stress test to provide an additional layer of diagnostic testing of the individual components on the path. 
   The above described logic of  FIGS. 3-13  provides isolation testing of different groups of the components of the path from a host to a storage device, which may include a fabric  10 . The path components tested together and in isolation include the host adaptor, any host adaptor FRUs, the fiber, any fabric ports and FRUs, and the storage device interface and any interface FRUs. The above described testing technique provides consistent testing of the SAN system to allow for consistent and dependable system diagnosis. 
   To initiate the diagnostic routine at block  200  in  FIG. 3 , the administrator would specify a path, i.e., a host adaptor and storage device interface through a user interface. The diagnostic test may be invoked from one of the hosts  2 ,  4 , or some other device in the system. When invoking the diagnostic test, the administrator may specify one or more of the following arguments to control the extent and operation of the diagnostic test:
         verbose command: causes the state machine  102  to display all messages to a screen display and log files.   silent command: instructs the state machine  102  to record all messages to log files only.   read only: performs only data safe reading while testing. This limits the extent of the testing as write operations are not performed during component diagnostics.   write-read: performs destructive write/read testing, allowing for all types of diagnostic testing.   quick: performs abbreviated testing.   aggressive: executes extensive testing.   everything: tests all qualified disks in a storage device that may be reached through a path. With this setting, during disk isolation all disks would be tested.   targeted: instructs the state machine  102  to only test specified disks during disk isolation and not all disks accessible through the specified storage device interface.   interactive: instructs the state machine  102  to allow the user to interact with the state machine to perform manual fault isolation. This arrangement causes the state machine to instruct the administrator to plug and unplug components as the rules evaluate the results to determine the faulty FRU.       

   Once the expert diagnostic tool  100  is invoked with the above arguments, the state machine  102  records a start record with a timestamp into the activity log and processes the rule base completely for each specified disk. When the state machine encounters the end of the rule base, it records the state of the tested storage path as COMPLETED or FAILED. If FAILED, the activity log records the name of the log(s) that contain failed test data, such as the suspect list  112 . These error log files contain important information that should accompany the failed component(s) back to the repair station, such as the suspect list  112  that indicates components that may be the source of the failure. 
   What follows are some alternative implementations for the preferred embodiments. 
   The described implementations may be implemented as a method, apparatus or article of manufacture using standard programming and/or engineering techniques to produce software, firmware, hardware, or any combination thereof. The term “article of manufacture” as used herein refers to code or logic implemented in hardware logic (e.g., an integrated circuit chip, Field Programmable Gate Array (FPGA), Application Specific Integrated Circuit (ASIC), etc.) or a computer readable medium (e.g., magnetic storage medium (e.g., hard disk drives, floppy disks, tape, etc.), optical storage (CD-ROMs, optical disks, etc.), volatile and non-volatile memory devices (e.g., EEPROMs, ROMs, PROMs, RAMs, DRAMs, SRAMs, firmware, programmable logic, etc.). Code in the computer readable medium is accessed and executed by a processor. The code in which preferred embodiments are implemented may further be accessible through a transmission media or from a file server over a network. In such cases, the article of manufacture in which the code is implemented may comprise a transmission media, such as a network transmission line, wireless transmission media, signals propagating through space, radio waves, infrared signals, etc. Of course, those skilled in the art will recognize that many modifications may be made to this configuration without departing from the scope of the present invention, and that the article of manufacture may comprise any information bearing medium known in the art. 
   In the discussed implementations, the flow of the diagnostic test logic is provided in a rule base object which references descriptors that specify one or more program modules to execute to implement the diagnostic testing. In additional embodiments, different program architectures may be used for the expert diagnostic tool to associate descriptors or program objects with different functions called according to the diagnostic test operations. 
   The diagnostic program may communicate requests for manual operations, e.g., disconnecting, removing and/or replacing components, through a displayable user interface, voice commands, printed requests or any other output technique known in the art for communicating information from a computer system to a person. 
   The described implementations referenced storage systems including GBICs, fabrics, and other SAN related components. In alternative embodiments, the storage system may comprise more or different types of replaceable units than those mentioned in the described implementations. Further, the diagnostic system may utilize different tests for different component types that are tested with the described diagnostic tool. 
   In the described implementations, the storage devices tested comprised hard disk drive storage units. Additionally, the tested storage devices may comprise tape systems, optical disk systems or any other storage system known in the art. Still further, the diagnostic tool may apply to storage networks using protocols other than the Fibre Channel protocol. 
   In the described implementations the system tested comprised a storage system. In alternative implementations, the system may include input/output (I/O) devices other than storage devices including an adaptor or interface for network communication, such that the described testing techniques can be applied to any network of I/O devices, not just storage systems. 
   In the described embodiments, the expert diagnostic software tool is executed from a host system. Additionally, the expert diagnostic tool may be executed from one of the storage devices or from another system. 
   In the described implementations, the tested system included only one switch between a host and storage device. In additional implementations, there may be multiple switches between the host and target storage device. In such case, each switch and component thereof on the path from the host and target storage device would have to be tested and diagnosed. 
   The foregoing description of various implementation of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention be limited not by this detailed description, but rather by the claims appended hereto. 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 hereinafter appended.