Abstract:
The present invention in at least some embodiments relates to improved methods and systems for governing access to SAN data storage devices (or simply “SAN devices”) employed in SAN systems. In some embodiments, the method involves storing a list at a SAN device. The list can be an exclusion list identifying devices that are not allowed to access the SAN device. During normal operation, the SAN device automatically contacts the SAN (or a component of the SAN, such as a SAN switch) to determine the identities of new devices that have entered into communication with the SAN. The SAN device then automatically updates the exclusion list to include those new devices such that, without further instructions, the SAN device is not accessible by those new devices. The method further can relate to the setup and failure recovery of SAN devices employed in SAN systems.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     FIELD OF THE INVENTION 
     The present invention relates to memory systems and, more particularly, to memory systems employing one or more storage area networks (SANs). 
     BACKGROUND OF THE INVENTION 
     It is often desirable that, at least in certain circumstances or at certain times, access to a given storage device coupled to a storage area network (SAN) be controlled, restricted or even entirely prevented. Allowing unintended access can be disadvantageous for a variety of reasons, including the reason that it might be inconsistent with maintaining desired levels of security or confidentiality. Yet even to the extent that some conventional SAN systems do provide some type of access control capability (many SAN systems entirely lack such a capability), such systems are still unsatisfactory. To begin with, such conventional SAN systems often are limited in their ability to control or restrict access to the storage devices on an ongoing basis after initial setup of the SAN system has occurred. Additionally, the setting up/configuration of such SAN systems tends to be complicated and to require significant time and effort on the part of technicians or other personnel. For example, in some cases, a manual intervention such as the switching of a physical switch by a human operation is necessary in order to allow a storage device to be accessed by other devices on the SAN. Also, some such conventional SAN systems tend to lack appropriate access control capabilities that are applicable in circumstances where a failure has occurred, e.g., a catastrophic failure associated with a power outage. 
     Therefore, for at least these reasons, it would be advantageous if improved methods of implementing/operating SAN systems (and corresponding improved SAN systems) could be developed. In particular, in at least some embodiments, it would be advantageous if SAN systems could be set up/configured so as to control or restrict the accessing of one or more storage devices on the SAN in an improved manner relative to conventional SAN systems. Additionally, in at least some embodiments, it would be advantageous if such access control capability could be provided on an ongoing basis even after installation of the storage devices with respect to the SAN had occurred, so as to allow for repeated modifications to any access restrictions. Further, in at least some embodiments, it would be advantageous if (notwithstanding the existence of such an access control capability), the SAN systems nevertheless could be set up and configured (and reconfigured) in a relatively easy manner, without a need for excessive effort on the part of technicians or other personnel in the form of manual intervention or otherwise. Additionally, in at least some embodiments, it would be advantageous if such SAN systems, upon the occurrence of failures, could be relatively easily reinstalled in a manner that largely or entirely maintained desired restrictions on access that existed prior to the failures. 
     BRIEF SUMMARY OF THE INVENTION 
     In at least some embodiments, the present invention relates to a method of governing access to a storage device connected to a storage area network (SAN). The method includes obtaining a first list, where access to the storage device by other devices is governed at least in part based upon the first list, and where each of the other devices is at least one of fully precluded from accessing the storage device, partly precluded from accessing the storage device, and allowed to access the storage device. The method additionally includes querying the SAN to determine if at least one additional other device has entered into communication with the SAN, and automatically updating the first list to reflect the at least one additional other device so that access to the storage device by the at least one additional other device is also governed at least in part based upon the first list. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram showing an improved SAN system in accordance with one exemplary embodiment of the present invention; 
         FIG. 2  is a flowchart showing exemplary steps of a method of operating the SAN system of  FIG. 1  in such a manner so as to achieve desired restrictions on the accessing of a given data storage device of the SAN system, in accordance with certain embodiments of the present invention; and 
         FIGS. 3A and 3B  are additional flowcharts showing exemplary steps of operation of the SAN system of  FIG. 1  relating to recovery of the SAN system subsequent to the occurrence of a failure, in accordance with certain embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Storage area networks (SANs) are networks that allow for the linking of multiple computer storage or memory devices with other devices such as computers (e.g., server computers). SANs in particular are useful for allowing numerous discrete data storage devices to be coupled for communication with, and to be accessed by, one or more other devices as if those numerous discrete storage devices were directly connected with the other devices requesting access (or even possibly as if those numerous discrete storage devices were a single integrated storage device). 
     Referring to  FIG. 1 , an exemplary SAN system  2  in accordance with one exemplary embodiment of the present invention includes SAN data storage devices  4  that are coupled by way of a SAN  6  to other devices  8 . In the present embodiment, the SAN  6  includes multiple communication links  10  and a SAN switch  12 . Each of the communication links  10  connects one (or, in alternative embodiments, more than one) of the SAN data storage devices  4  or the other devices  8  with the SAN switch  12 . Although in the present embodiment, the SAN  6  includes the communication links  10  and the SAN switch  12 , in alternate embodiments the SAN  6  could also take on other forms or have other structures than those shown. 
     Each of the SAN data storage devices  4  is intended to be representative of any of a number of different types of storage devices, for example, disk storage devices such as hard disk drives or CD-ROM devices, tape data storage devices (e.g., tape libraries), virtual tape libraries (which are disk-based libraries) and a variety of other storage devices. The other devices  8  are intended to be representative of any of a variety of different types of devices that can be coupled to a SAN such as the SAN  6 , so as to access information stored at one or more of the storage devices  4 . For example, one or more of the other devices  8  could be computers (e.g., server computers) or other controllers, operator interface terminals such as workstations, or even additional data storage devices that are attempting to access one or more of the data storage devices  4 . 
     The SAN  6  is capable of operating in a manner that allows the multiple data storage devices  4  to be accessed by the other devices  8  in a seamless or almost seamless manner such that the data storage devices  4  largely can be viewed as being directly accessible or directly connected to each of the other devices  8  (also, in some cases, the SAN  6  makes it appear that the data storage devices  4  are acting as a single data storage device). Although three data storage devices  4  are shown in  FIG. 1 , the SAN system  2  is intended to be representative of a variety of SAN systems that include any number of data storage devices ranging from only one data storage device to many more than three data storage devices. Likewise, the SAN system  2  is intended to be representative of a variety of SAN systems that include any one or more other devices that are attempting to access information stored at one or more storage devices that are connected to the SAN. 
     As shown, in the present embodiment the SAN switch  12  keeps track of the SAN data storage devices  4  and other devices  8  that are connected to the SAN  6 . In particular, the SAN switch  12  includes a memory device (or memory devices)  14  that stores a list  16  of all of the other devices  8  that are in communication with the SAN  6 . Thus, in the present embodiment, the list  16  includes six names (or “unique identifiers”) corresponding to the six other devices  8  (namely, Wwpn-1 . . . Wwpn-6). The SAN switch  12  updates the list  16  as the identities and number of the other devices  8  varies over time. This function of the SAN switch  12  of keeping track of the devices attached to the SAN  6  in some embodiments can be termed a Simplified Naming Service (SNS). 
     In accordance with the present embodiment of the invention, a first of the SAN data storage devices  4 , namely the SAN data storage device  18 , also includes one or more memory devices  20 . In the present embodiment, the memory device(s)  20  are separate from a primary data storage medium (or media)  21  of the SAN data storage device  18  that provides the primary data storage capacity of the data storage device albeit, in other embodiments, the memory device(s)  20  can form merely a portion of the primary data storage medium  21  (or both the memory device and medium  21  can form subportions of a single memory device). In some embodiments, the memory device(s)  20  are one or more caches associated with the storage device  18 . 
     Further as shown, the storage device  18  includes a control device  23 , which can be, for example, a microprocessor, a computer, a programmable logic controller, or other control device. The control device  23  is coupled to each of the memory device(s)  20  and the primary data storage medium  21  by one or more control lines. As described in further detail below, the control device  23  governs, based at least in part upon the contents of the memory device(s)  20 , whether the storage device  18  will provide data from the primary data storage medium  21  onto the SAN  6  in response to requests received from the other devices  8  via the SAN. Although the present discussion focuses upon the operation of the first SAN data storage device  18  as an example, it should be understood that each of the other data storage devices  4  also can employ one or more memory device(s) such as the memory device  20  as well as primary data storage media  21  and control device  23 , and operate in the same (or largely the same) manner as the data storage device  18 . 
     As shown, the memory device  20  of the first SAN data storage device  18  stores information relating to the identities and number of the other devices  8 . In particular, the memory device  20  stores a first list  22  of all of the other devices  8 . The list  22  is intended to be identical to the list  16  stored on the SAN switch  12 , albeit in the present embodiment the storage device  18  only queries the SAN switch  12  on a periodic basis, such that in certain cases when one or more of the other devices  8  are removed from the SAN  6  or new such devices are coupled to the SAN, the list  16  is updated but the list  22  is not yet updated until a later time. 
     In addition to the list  22 , the memory device  20  also stores a second list  24  that in the present embodiment is an exclusion list. The exclusion list  24  lists one or more of the other devices  8  (or, in certain cases, does not list any of the other devices, at least at certain times) that are to be prevented from accessing the first SAN data storage device  18 . As indicated by the exemplary exclusion list  24  shown in  FIG. 1 , the exclusion list often lists a subset (e.g., two out of the six) of the other devices  8 . In the present embodiment, the contents of the exclusion list  24  are initially set (typically when the first SAN data storage device  18  is first coupled to the SAN  6 ) by a technician or other human operator by way of a user interface  26  that is coupled to the storage device  18  by way of a communication link  28 . 
     Although the user interface  26  can be employed to initially set the contents of the exclusion list  24 , in the present embodiment the contents of the exclusion list  24  can also be updated or changed on a periodic, continuous or other basis in response to further commands or information provided via the user interface  26 . That is, a human operator by way of the user interface  26  can change, at any time, the set of other devices  8  that are precluded from accessing the data storage device  18 . The setting, updating, or modifying of the contents of the lists  22 , 24  is discussed in further detail with reference to  FIGS. 2 ,  3 A and  3 B. 
     The user interface  26  can take a variety of forms depending upon the embodiment. For example, the user interface  26  can be a standard “Wintel” computer having input and output devices such as a monitor, keyboard, mouse or other devices (e.g., a touch screen). The user interface  26  can also include, for example, a graphical user interface (GUI) or a command line interface. The communication link  28  can take a variety of forms including, for example, a dedicated wire line and a wireless connection. In some embodiments, the user interface also can be replaced with some other control device (e.g., one not requiring human interaction). For example, in some embodiments, the initial specifying of the exclusion list is determined automatically, without any immediate human involvement, while changes to the exclusion occur at least sometimes in response to commands provided via the user interface  26 . 
     As described in further detail with reference to  FIGS. 3A and 3B , in at least some embodiments including the present embodiment, the first SAN data storage device  18  also is coupled by way of a communication link  30  to a backup memory device  32 , which stores (depending upon the embodiment) one or both of the lists  22 ,  24 . The backup memory device  32  and communication link  30  can include any of a variety of different structures. For example, the backup memory device  32  could be one of the other devices  8  such as a SAN based disk, a dedicated additional storage device, a LAN-based storage location, or any of a variety of other memory/storage devices located locally or remotely with respect to the storage device  18 . Also for example, the communication link  30  (like the link  28 ) can be a dedicated wire link that hardwires the backup memory device  32  to the first SAN data storage device  18 , or a wireless connection. 
     Although not shown in  FIG. 1 , in alternate embodiments it is possible that the storage device  18  can be in communication, directly or indirectly, with one or more informational devices other than the SAN switch  12  (or other portion of the SAN  6 ) in order to obtain information (e.g., attributes) regarding the storage devices  4  and other devices  8  that are connected to or in communication with the SAN. Such an informational device can, but need not, be termed a “repository” of information regarding the devices that are connected to the SAN. Depending upon the embodiment, such an informational device could take any of a variety of different forms, could be coupled to the storage device  18  in any of a variety of different manners, and could be (but need not be) directly coupled to the SAN  6  itself. For example, such a repository could include one of the other devices  8 , the user interface  26 , or a remote device. Also, such a repository could be coupled to the storage device  18  directly or indirectly by way of a LAN, a communication link operating in accordance with the Storage Management Initiative Specification (SMIS), or other communication link(s) including possibly the SAN itself. 
     Depending upon the embodiment or configuration, the information supplied by a repository could be used in a variety of ways. For example, the information supplied by a repository could serve as a basis for making determinations regarding the granting of security access. Further for example, in certain circumstances, the information supplied by a repository could allow for making access decisions at a finer granularity (e.g., allowing for different levels of access or varying access decisions based upon a variety of different considerations) than would otherwise be the case. In some circumstances, access decisions could be based upon policies combining one or more of the attributes (or other information) retrieved from a repository. 
     Turning to  FIG. 2 , a flowchart  34  shows exemplary steps of operation of the SAN system  2  of  FIG. 1  in accordance with at least some embodiments of the present invention. In particular, steps of operation relating to the initial setting up of the first SAN data storage device  18  in relation to the rest of the SAN system  2 , and then continued operation of the SAN system thereafter, are shown. As shown, upon starting at a step  36 , at a step  38  the first SAN data storage device  18  is connected to the SAN  6 . At a step  40 , the storage device  18  queries the SAN switch  12  as to the devices (specifically, the other devices  8 ) that are currently logged in with respect to the SAN  6 , that is, the devices identified in the list  16  stored on the SAN switch  12 . 
     Next, at a step  42 , the storage device  18  stores in its own memory device  20  the first list  22  of devices that are currently logged in. The first list  22  stored on the memory device  20  is identical to that the list  16  currently existing on the SAN switch  12 . Further, at a step  44 , the storage device  18  then receives additional information regarding a list of devices to be excluded in terms of being able to access the storage device  18 . As discussed above with respect to  FIG. 1 , this exclusion list  24  can be provided from any of a variety of sources and, in the present embodiment, is provided by a technician or other operator via the user interface  26 . 
     Upon the execution of step  44 , the initialization or setup procedure in terms of connecting the storage device  18  to the SAN  6  and configuring the storage device for operation is completed. Once the storage device  18  is initialized and operational, the storage device is then capable of receiving requests via the SAN  6  from one or more of the other devices  8 . Thus, at a step  46 , the storage device  18  receives a request in which one of the other devices  8  is attempting to access the storage device to obtain a portion of data stored within that device (e.g., stored within the primary data storage medium  21 ). Upon receiving such a request, the storage device  18  consults the exclusion list  24  stored on its memory device  20  at a step  48  to determine whether the other device  8  making the request is on the exclusion list. 
     If the requesting device is not on the exclusion list  24 , then the storage device  18  performs the requested action at a step  50 , that is, the storage device provides the requested data to the requesting device over the SAN  6 . Upon completing the requested action at step  50 , the storage device  18  considers whether it is time to update the list  22  regarding devices on the SAN at a step  52 . If the storage device  18  at step  48  determines that the requesting device is on the exclusion list  24 , then the storage device declines to perform the requested action and immediately proceeds from step  48  to step  52 . 
     Assuming that, at step  52 , it is not yet time to update the list  22 , then the storage device  18  again is available to receive additional requests and returns to step  46 . If, however, at step  52  it is determined that it is time to update the list  22  of devices on the SAN  6 , the storage device  18  requeries the SAN switch  12  at a step  54  regarding the other devices  8  that are currently logged in with respect to the SAN  6 . Whether it is time to update the list  22  can be determined in a variety of ways, for example, simply based upon whether a certain amount of time (e.g., several hundred milliseconds) has elapsed since the previous updating of the list. 
     Upon requerying the SAN switch  12 , at a step  56  the storage device  18  receives a current (or updated) device list corresponding to the list  16  on the SAN switch  12  and compares the received current device list to the existing version of the list  22  stored on the memory device  20 . If at a step  58  it is determined that there exists some difference between the current device list received from the SAN switch  12  and the list  22  stored on the memory device  20 , then the storage device  18  proceeds to update the exclusion list  24  to include any devices on the received current device list that are not on the list  22  stored on the memory device  20 . 
     Thus, if any additional other devices  8  have been added to the SAN system  2  since the previous time at which the SAN switch  12  was consulted regarding the identities of the other devices  8 , the identifiers/names of those newly-added devices are automatically added to the exclusion list  24 . Likewise, if one or more of the other devices  8  no longer are connected to the SAN  6 , the exclusion list  24  also is updated to remove the identifiers/names of those devices that have been removed. 
     Upon such adjustment of the exclusion list  24 , the storage device  18  at a step  62  also updates the list  22  to reflect the current devices that are on the SAN  6  in accordance with the newly-received information from the SAN switch  12 , and then proceeds to step  64 . Also, if at step  58  it is determined that there does not exist any difference between the current list of devices received from the SAN switch  12  and the list  22  of devices stored on the memory device  20 , then the storage device  18  merely proceeds to step  64  without performing any updating of the exclusion list  24  or the list  22  of devices. 
     Upon reaching step  64 , the storage device  18  also determines whether any command has been provided from another source (e.g., from the user interface  26 ) to otherwise modify the exclusion list  24  (or even possibly the list  22  of devices). If such a command is provided, then the exclusion list  24  is updated accordingly at a step  66  while, if not, no update occurs. In either case, the storage device  18  then returns to step  46  to receive additional requests. 
     Through operation of the process shown in  FIG. 2 , access to the storage device  18  (or any of the storage devices  4 ) can be governed on an ongoing basis. Due to the periodic requerying of the SAN switch  12  by the storage device  18 , changes in the identities and number of devices connected to the SAN  6  are automatically identified, allowing for automatic updating of the exclusion list  24 , such that the addition of new devices onto the SAN does not result in unintended accessing of the storage device by those new devices. At the same time, the governing of access to the storage device  18 , as well as the updating of the exclusion list  24 , can be accomplished in a manner requiring only limited amounts of operator attention. Initial setup, as well as continued control over the operation of the storage device  18  in connection with the SAN  6  can be achieved with relative ease and at low cost. 
     Turning to  FIGS. 3A and 3B , in accordance with at least some embodiments of the present invention, the operation of the storage device  18  in relation to other components of the SAN system  2  can take one of two forms after a failure has occurred such that one or both of the lists  22 ,  24  of the memory device  20  have been lost (e.g., due to a power outage or the like).  FIG. 3A  shows a first flowchart  68  in which the storage device  18  is reinitialized by consulting the backup memory device  32  to obtain exclusion list information (e.g., information corresponding to the list  24 ) that was stored in the backup memory device, while  FIG. 3B  shows a second flowchart  80  in which the storage device  18  is reinitialized based upon both exclusion list information and device list information (e.g., information corresponding to the list  22 ) obtained from the backup memory device  32 . Regardless of whether the steps shown in  FIG. 3A  or  FIG. 3B  are followed, upon performing such recovery steps, the storage device  18 /SAN system  2  returns to a point A shown in  FIG. 2 , that is, to step  46  at which the storage device is then in a position to receive requests from the other devices  8  on the SAN  6 . 
     Turning to  FIG. 3A  in particular, upon starting at a step  70 , it is first determined that a failure (e.g., a power outage) has ended at a step  72 . Then, at a step  74 , the storage device  18  obtains stored exclusion list information from the backup memory device  32  and stores the information in the memory device  20  as the exclusion list  24 . Upon the restoring of the exclusion list information within the memory device  20 , at a step  76  the storage device  18  queries the SAN switch  12  regarding the devices that are currently logged in with respect to the SAN  6 . Finally, the storage device  18  at a step  78  stores the list of devices currently logged in as provided by the SAN switch  12 , after which the storage device  18  then returns to point A. 
     In contrast, with respect to  FIG. 3B , upon starting at a step  82 , and further upon determining that the failure has ended at a step  84 , the storage device  18  then obtains both stored device list information and exclusion list information from the backup memory device  32  and based upon that information restores the first and second lists  22 , 24 , at a step  86 . Then, at a step  88 , the storage device  18  queries the SAN switch  12  regarding the devices that are currently logged in with respect to the SAN  6 . At a step  90 , the storage device  18  then determines whether there is any difference between the stored device list information received from the backup memory device  32  and the information received from the SAN switch  12 . 
     If there is such a difference, the exclusion list  24  is updated, at a step  92 , to include any devices that are currently logged in with respect to the SAN  6  that were not included in the stored device list information that was obtained form the backup memory device  32 . At a step  94 , the list  22  of the storage device  18  is then updated to reflect the current information received from the SAN switch  12 , after which the process is at point A. However, if at step  90  it is determined that there is no difference between the stored device list information received from the backup memory device  32  and the current information received from the SAN switch  12 , then the storage device  18  proceeds from step  90  directly to point A. 
     Regardless of whether the flowchart  68  or the flowchart  80  is followed by the storage device  18 /SAN system  2 , the result of the process is largely the same insofar as, after the failure, the storage device  18  is configured so that all of the devices that were precluded from accessing the storage device prior to the failure presumptively remain excluded. However, in the case of  FIG. 3A , there is no adjustment to the exclusion list made to reflect any changes in the devices that are coupled to the SAN  6  that may have occurred between the time of the failure and the time of the recovery. In contrast, with respect to  FIG. 3B , any other devices that are newly added during the failure are automatically added to the exclusion list. It should also be noted that, in either case, an operator still has the option of further adjusting the exclusion list notwithstanding these automatic operations (e.g., in accordance with steps  64  and  66  of  FIG. 2 ). 
     In at least some embodiments, the presently-described processes (or variations thereof) also can be used to allow a user to completely delete a current snapshot of the SAN environment and then to respecify those devices that are connected to the SAN  6 , for example, by requerying the SAN switch  12  for the new current set of devices logged into the SAN. At the same time, the exclusion list could be completely changed/overwritten so as to not include any of the devices logged into the SAN  6 . As a result, in at least some embodiments of the present invention, a methodology of quickly granting access to large numbers of newly added devices on the SAN  6  is achieved. 
     Although the above discussion concerning  FIGS. 1 ,  2 ,  3 A and  3 B describe certain embodiments of the present invention, it should be understood that numerous variations to the system and processes described above are also intended to be encompassed within the present invention. For example, in certain embodiments, rather than (or in addition to) the exclusion list  24 , the storage device  18  can instead (or also) store a granted list identifying those of the other devices  8  that are allowed to access the storage device. In a system employing only a granted list (as opposed to an exclusion list), only those devices that were on the granted list would be allowed to gain access to the storage device, and any devices not on the granted list would be denied access. 
     Also for example, while the above discussion concerning the FIGS. particularly focuses upon the obtaining/retrieving of information from the SAN  6  (e.g., the SAN switch  12 ), the backup memory device  32 , and/or the user interface  26 , in alternate embodiments information could instead or additionally be obtained from one or more alternate devises or “repositories” such as those discussed above. That is, one or more “repositories” or similar devices could serve as sources of information regarding the names/identities/attributes of devices on the SAN as well as other lists such as exclusion lists. Through the use of such information (e.g., attributes) received from such repositories, it would be possible to determine a variety of levels of access, or otherwise to make decisions on allowing access based upon a variety of considerations. 
     Additionally, while certain embodiments employ exclusion and/or granted lists, additional embodiments could employ multiple lists (or arrays or other organized information, all of which can be generally understood to constitute “lists” in a general sense) identifying devices having varying degrees or levels of access. For example, the storage device  18  could have (instead of or in addition to an exclusion list and/or a granted list) a “partial granted” list that would identify devices that could access the storage device only under certain circumstances. Also for example, the storage device  18  could have multiple lists including multiple partial exclusion or partial granted lists, each of which identified devices that could not or could access the storage device (or portions of the storage device) under various circumstances or at various times. Further, although in the present embodiment the SAN  6  is described as including the SAN switch  12  that keeps track of the devices that are logged onto the SAN, in alternate embodiments another manner of keeping track of the devices connected to the SAN could be employed. 
     As discussed, various embodiments of the present invention are capable of providing (depending upon the embodiment) one or more advantages in comparison with many conventional systems. For example, certain embodiments of the present invention allow for relatively easy initialization of SAN data storage devices onto a SAN system. Additionally, certain embodiments of the present invention allow for significant control to be exercised over which devices can access the SAN data storage devices, with such control being variable over time, on an ongoing basis. Further, not only can such control over access be varied over time due to automatic updating of the information stored on the storage device, but also such control can be governed by user commands (or commands received from other sources, such as other computers). 
     Such access control, as can be provided by various embodiments of the present invention, can be helpful in a variety of circumstances. For example, the particular information stored on a given storage device in some circumstances is confidential or appropriate only for certain parties having a security clearance, and in such circumstances it therefore can be desirable to restrict access to the given storage device. Also, it can be desirable to create/modify access restrictions when changes occur to a SAN system, for example, when new devices are added to the system. Additionally, in at least some embodiments of the present invention, recovery from failures (even catastrophic failures or disasters) can be achieved with relatively little effort, and in a manner that maintains much if not all control over access to the SAN data storage device. 
     It is specifically intended that the present invention not be limited to the embodiments and illustrations contained herein, but include modified forms of those embodiments including portions of the embodiments and combinations of elements of different embodiments as come within the scope of the following claims.