# Patent

## Title
Method and apparatus for identifying storage devices

## Abstract

Embodiments according to the invention perform functions including discovery, classification, and profiling of storage devices, computer systems, connection elements, and other components relating to a storage area network (SAN). Changes to the SAN topology are tracked in order to show growth patterns.

## Background
CROSS-REFERENCES TO RELATED APPLICATIONS
The present application claims priority from the following U.S. Provisional application: U.S. Application No. 60/268,694, filed Feb. 13, 2001 and titled “Virtual Storage Systems which is incorporated herein by reference for all purposes.


STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
NOT APPLICABLE
REFERENCE TO A “SEQUENCE LISTING,” A TABLE, OR A COMPUTER PROGRAM LISTING APPENDIX SUBMITTED ON A COMPACT DISK
NOT APPLICABLE
BACKGROUND OF THE INVENTION
The present invention relates generally to computer storage and in particular to identifying information about those elements which constitute a storage area network.
Knowledge is an important competitive advantage for any business. The drive to develop knowledge stores and improve storage hardware capacity leads to explosive growth in storage and computing resources. As a consequence of businesses depending increasingly on applications and their underlying data, continuous, reliable, and rapid access to data becomes critical. It is important to be able to guarantee online access and quick restores of lost data. Mass storage systems are becoming increasingly complex as developments in storage technology continue to meet the demands of the market.
A natural evolutionary trend in the provision and management of mass storage systems has been the development of storage area networks (SANs). SAN is a storage architecture which provides high capacity storage capability that is accessed reliably and transparently by users. The architecture virtualizes physical disks into a large consolidated pool and then presents the individual users (web servers, enterprise servers, PC users, an so on) with virtual disks from the pool.
SAN architectures typically comprise a collection of various storage technologies, each having different capabilities optimized for specific situations; e.g., individual disks, arrays such as RAID (redundant array of inexpensive disks) and JBOD (just a bunch of disks), tape drives, and so on. Fibre channel switches are typically used to connect computer users (servers, PC users, etc.) to the storage devices.
Allocating storage for an application, such as a database running on a server, is a complex and error-prone process. Usually, it requires the system administrator to know the details of what storage device(s) would be the right match for the particular application. Obtaining knowledge about such details as throughput, access time, multi-path policy, reliability, and availability is a process which invariably relies on the individual expertise of one person or another.
In addition, business organizations sharing a single large SAN typically use a fibre channel switches' port zoning capability to zone off, or hide, one organizations devices from another organizations devices. Zoning is done a switch at a time. This becomes complex as switch after switch is added to the SAN.
BRIEF SUMMARY OF THE INVENTION
Embodiments in accordance with the invention provide an automated system and method for discovering functional capabilities of elements which comprise a SAN (storage area network). The information is obtained by categorizing each SAN device by attributes, functions and capabilities. The information is of interest for the purpose of storage configuration and management, and is used to intelligently match server storage requests to storage devices, thereby simplifying SAN storage management.
An aspect of the invention provides different divisions in a large enterprise to share the same SAN by assigning a user domain to each physical SAN element. Only users whose domain identifier matches the assigned domain identifier can access that SAN element.
Information provided in accordance with the invention addresses problems in another area of SAN management, namely inventory control and data center growth planning. Tools are provided for discovering and displaying the physical topology of a SAN to facilitate periodic monitoring to identify changes in a SAN. Processing in accordance with an illustrative embodiment of the invention involves periodically creating a baseline of physical topology as specified by a user policy, comparing that baseline to the previous baseline, and generating reports showing base inventory and various growth patterns, such as amount of new disk storage and so on.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a high level generalized illustration of a storage area network including a storage server according to an embodiment of the present invention;
FIG. 2A shows a high level block diagram of hardware components in the storage server according to an embodiment of the present invention;
FIG. 2B illustrates a general block diagram of management functions in the storage server according to an embodiment of the present invention;
FIG. 3 is a block diagram illustrating the high level components of Discovery processing in accordance with an embodiment of the present invention;
FIG. 4 is a data flow diagram showing a flow of information during Discovery processing according to an embodiment of the present invention;
FIG. 5 is data flow diagram showing a flow of information during a process which occurs subsequent to Discovery processing in accordance with an embodiment of the present invention;
FIG. 6 is a data flow diagram illustrating a flow of information while configuring storage in a storage processor;
FIG. 7 illustrates administration activity according to an embodiment of the present invention;
FIG. 8 shows a sequence diagram of Discovery processing according to an embodiment of the invention;
FIG. 9 shows a sequence diagram of device removal in accordance with an embodiment of the present invention;
FIG. 10 shows a state transition diagram for SCSI device processing according to an embodiment of the present invention;
FIG. 11 shows a state transition diagram for SCSI bring-up processing in accordance with the invention;
FIG. 12 shows a state transition diagram for HBA processing in accordance with the invention; and
FIG. 13 shows a state transition diagram for PATH discovery processing in accordance with the invention.



DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a storage server 100 according to an embodiment of the present invention. The figure also shows a storage area network (SAN) 102, a number of physical storage devices 104, and a number of host computers 106. The storage server 100 is also referred to as a Virtual Storage Exchange (VSX) and is further detailed in FIGS. 2A–2B.
The SAN 102 can be any type of computer network. It is referred to as a storage area network in the present application because that is its relevant function with respect to the embodiments of the present invention. In an embodiment of the present invention, the SAN 102 is a Fibre Channel network, the host computers 106 and the storage devices 102 are configured to communicate with a Fibre Channel network, and the storage server 100 is also configured to communicate with a Fibre Channel network. Thus, the storage server 100 can be easily added to an existing SAN.
The physical storage devices 104 include tape drives, disk arrays, JBODs (“just a bunch of disks”), or other types of data storage devices. The physical storage devices 104 can be connected directly to the host computers 106 via the SAN 102 or can be indirectly connected to the host computers 106 via the SAN 102 and the storage server 100. It has been observed that management of storage virtualization is burdensome when the storage devices 104 are directly connected to the host computers 106 via the SAN 102. The present invention improves management of storage virtualization by using the storage server 100 to indirectly connect the storage devices 104 to the host computers 106.
The host computers 106 can be servers or stand-alone computers. The host computers 106 can be directly connected to the SAN 102 or indirectly connected via a switch, router, or other communication link.
FIG. 2A is a block diagram of the storage server 100 showing the hardware components related to embodiments of the present invention, including a storage processor 110, a line card 112, a virtual server card 114, and a switch fabric 116.
The storage server 100 may include one or more storage processors 110 (SP). The storage processors 110 process the storage commands and data to be stored as information flows between the host computers 106 and the storage devices 104. One or more of the storage processors 110 may be included on each line card 112 (LC). The storage server 100 includes space for numerous line cards 112, so the capabilities of the storage server 100 can be modularly increased by adding more line cards 112 or more storage processors 110. Each storage processor 110 is associated with one or more ports of the storage server 100.
The storage server 100 may include one or more virtual server cards 114 (VSC). The virtual server cards control the operation of the storage server 100 and control the line cards 112, which perform the actual work of transferring commands and data.
The switch fabric 116 connects the storage processors 110. The switch fabric switches information received at one port to another port of the storage server 100. For example, when a host computer 106 wants to read data stored on the storage area network 102, its request is processed by the storage processor 110 associated with the port associated with that host computer 106. That storage processor 110 is referred to as the upstream storage processor 110. The upstream storage processor 110 communicates with a downstream storage processor 110 associated with the port associated with the storage device 104 storing the data to be read, via the switch fabric 116. Then the switch fabric 116 transfers the data read from the storage device to the host computer 106, via the downstream and upstream storage processors 110.
FIG. 2B is a block diagram of the storage server 100 showing the functionality relevant to embodiments of the present invention. The functions of the storage server 100 may be implemented by one or more processors that execute processing according to one or more computer programs, microcode segments, hardware structures, or combinations thereof. The functions relevant to the present invention are the media unit (MU) manager 120, the virtual logical unit number (virtual LUN or VLUN) manager 122, the physical logical unit number (physical LUN or PLUN) manager 124, and the Host Manager 126. The Host Manager provides two basic functions. First, it maintains customer information about the physical topology of Hosts in the SAN and maps HBAs found by the Discovery Manager to the Host, as required by the customer. Hosts can be grouped into clusters to help manage shared, or clustered, storage. Once the physical topology is described to the Host Service, the Host Service becomes the consumer of exported storage.
Additional details of the storage server 100 are disclosed in U.S. Provisional Application No. 60/268,694 and in the following co-pending, commonly owned U.S. patent applications: U.S. patent application Ser. No. 10/077,696, filed Feb. 13, 2002, titled Silicon Based Storage Virtualization Server; U.S. patent application Ser. No. 10/076,855, filed Feb. 13, 2002, titled Storage Virtualization and Storage Management to Provide Higher Level Storage Services; U.S. patent application Ser. No. 10/076,909, filed Feb. 13, 2002, titled Method and Apparatus for Identifying Storage; U.S. patent application Ser. No. 10/077,181, filed Feb. 13, 2002, titled System and Method for Policy Based Storage Provisioning and Management; U.S. patent application Ser. No. 10/077,181, filed Feb. 13, 2002, titled “Virtual Data Center; U.S. patent application Ser. No. 10/076,906, filed Feb. 13, 2002, titled Failover Processing in a Storage System; U.S. patent application Ser. No. 10/077,199, filed Feb. 13, 2002, titled RAID at Wire Speed; U.S. patent application Ser. No. 10/076,878, filed Feb. 13, 2002, titled Method for Device Security in a Heterogeneous Storage Network Environment; all of which are incorporated herein by reference for all purposes.
The PLUN manager 124 manages data and command transfer to and from the storage devices 104. Each storage device 104 may have associated therewith a PLUN that is used for identifying each particular storage device 104. Typically, a physical device is associated with one PLUN. However, depending on the sophistication of the storage device, the physical device may have more than one PLUN associated with it. Each PLUN in such a situation represents a different physical storage space in the storage device.
The VLUN manager 122 manages data and command transfer to and from the host computers 106. Each host computer 106 may be associated with one or more VLUNs. Each VLUN represents a virtual address space (e.g., gigabytes of storage) with defined attributes (e.g., performance parameters, reliability level, etc.). As such, each host computer 106 exchanges data and commands with the storage server 100 with reference to a particular VLUN.
The MU manager 120 basically translates between VLUNs and PLUNs. The MU manager 120 is responsible for managing the address space of all the storage devices 104 (physical LUNs) connected to the storage server 100. The MU manager 120 also manages the address space of the storage constructs built within the storage server 100, including slices, concatenations, RAID0 (stripes) and RAID1 (mirrors).
The MU manager 120 uses an abstract block-storage addressing technique that enables address spaces to be treated in a logical manner, regardless of the underlying storage constructs or physical LUNs. These logical address spaces can be combined together into more complex and feature rich storage constructs, which are also treated simply as abstract block-storage address spaces.
Used in conjunction with a virtual LUN, these logical address spaces can be configured to appear as LUNs on a multi-ported storage device. This process of presenting physical LUNs as logical address spaces on virtual devices is referred to as storage virtualization.
A function of the VSX is to centralize the management layer in the SAN. It organizes the connections, storage elements, and computer systems into abstract relationships in order to facilitate secure and robust data transfer. Every time the SAN changes (e.g., topology is altered, devices are added or removed) or when the VSX initializes it must perform an operation referred to as network discovery. Discovery is the act of finding or locating something, and obtaining additional information about it. Such discovery begins at the port level and ends at the services level.
All devices derive from the SAN element. All SAN devices attach to the network by means of a port interconnect. Device discovery begins at the port level Some ports belong to connection devices such as fibre channel hubs, switches, and bridges. Such connection devices provide device-specific methods to discover what is attached to them. As the connection devices are traversed, the discovery process can ascertain the SAN topology.
Other ports permit process images to execute on them. Certain process images work together to facilitate a protocol, e.g., the SCSI (small computer systems interface) protocol. The SCSI protocol is facilitated by a SCSI target process executing on one port and a SCSI initiator process executing on another port.
The next level of discovery involves SCSI initiators and targets. The SCSI standard identifies many types of target devices. SCSI tape, array controller, magnetic disk are a few examples. Discovery functions place all target device types not supported into an unsupported table.
Supported devices are grouped into two categories: the qualified device category and the unqualified device category. A qualified device is a device which satisfies certain rules which test whether the device can operate with the VSX. For example, one rule might require that the block size of the device be 512 bytes. Another rule might require the device uses the SCSI Version 3 interface. An unqualified device may nonetheless be operable with the VSX. However, such a determination will typically require testing to determine compatibility. All qualified devices are initialized by the discovery process and announced to the storage configuration abstraction layers. All unqualified devices are brought up, should a default handler exist. Otherwise, the unqualified device is moved to the unsupported category.
During a device bring-up step, the discovery method uses standard SCSI commands to determine a device's reliability, availability, failover behavior, command support, access time, and throughput. Discovery then groups all discovered SAN devices, by attribute, and presents them to application software.
The Discovery Service is primarily responsible for propagating the Ports, Paths, Devices, and Physical LUNs (PLUNs) visible to all the Network Processors in a VSX into the Database. Discovery is initiated every time a card is powered on. Discovery can be performed on a system-wide basis, a card basis, or a port basis.
FIG. 3 shows a block diagram of the Discovery Services according to this illustrative embodiment of the present invention. Discovery is loosely layered into four software components: the Discovery Manager 302, the Discovered Object Managers 320, Basic Discovery 304, and the Discovery Agent 308.
The Discovery Manager 302 is responsible for coordinating the discovery process and managing the consolidated discovery database. Basic Discovery 304 manages information passing between the Discovery Manager, Discovered Object Managers, and Discovery Agents.
Discovered Object Managers 320 are responsible for initializing the discovered device and making the device ready for other services. There is a Discovered Object Manager for each of kind of device that can be discovered. As can be seen in FIG. 3, there is a SCSI Device Manager 322 to manage SCSI devices. A Switch Manager 324 manages switch objects (e.g., a host bus adapter HBA) and a Path Manager 326 manages path elements of the SAN.
The Discovery Agent 308 manages the SAN infrastructure details 334. An instance of the Discovery Manager runs in each VSC. An instance of Basic Discovery runs in both VSC and LC. The Discovered Object Managers are split between VSC and LC. An instance of the Discovery Agent runs in each SP (storage processor).
Each Discovered Object requires its own Object Manager, although some Discovered Objects might share an Object Manager. The following is a list of SAN elements and their respective Managers:

    
    
        SCSI Device Manager—Manages the initialization and presentation of SCSI devices.
        
            SSC Sequential-access device—Manages generic magnetic tape devices.
            SSC Printer device—Manages generic printer devices.
            SPC Processor device—Manages generic processor devices.
            SBC Write-once device—Manages some optical disks.
            MMC CD-ROM device—Manages CD-ROM devices.
            SGC Scanner device—Manages scanner devices.
            SBC Optical memory device—Manages some optical disks.
            SMC Medium changer device—Manages jukeboxes.
            SSC Communications device—Manages some communication devices.
            ASC IT8—Manages Graphic arts pre-press devices.
            SCC Storage array controller device—Manages RAID devices.
            SES Enclosure services device—Manages SES devices.
            Direct-access device—Manages generic magnetic disk type devices.
            RAID—Manages Direct-Access devices that are known to be RAID controllers.
            Reserved—Manages reserved devices.
            Unknown or no device type—Manages unknown device types.
        
        
        Unsupported Device Manager—Manages devices for which the VSX is not qualified.
        Host Manager—Manages Servers mapped to HBAs.
        Port Manager—Manages both HBAs and SP ports.
        Path Managers—There are two Path Managers
        
            Host Path Manager—Manages a connection from a SP port to a Server port.
            Device Path Manager—Manages a connection from a SP port to a storage port.
        
        
        Switch Manager—Manages Fibre Channel switches.
        VSX Manager—Manages other VSXs in a VSX cluster.
        HUB Manager—Manages Fibre Channel HUBS.
        SCSI Bridge Manager—Manages Fibre Channel to SCSI Bridges.
        LAN Bridge Manager—Manages Fibre Channel to LAN Bridges.
        WAN Bridge Manager—Manages Fibre Channel to WAN Bridges.
    
    


Following is a partial list of attributes for discovered objects. Attributes define particular characteristic(s) of the device. All SAN elements have a Location, HA Set ID, User Domain, and ID. The ID will be a Confluence identifier, which maps a device-specific ID to a VSX Device ID. The user will assign the User Domain, Location, Department, and HA Set ID. In the absence of a user-assigned value, the default User Domain will be “Administrator”, and the default values for all other attributes will be “Unassigned”. Discovery should facilitate the assignment of these user-supplied values during installation.

    
    
        SCSI Device/Physical LUN (PLUN) Attributes
        
            Vendor
            Model
            Serial Number
            Code Revision
            Block Size
            Capacity in blocks
            Transfer Rate
            RPM
            Multi-port information
            Cache Size
            Location
            Department
            User domain
            HA Set ID
            Tuning Parameters
            Security capabilities
            WWN
        
        
        Unknown SCSI Device Attributes
        
            Location
            User domain
            HA Set ID
        
        
        Host Attributes
        
            Name
            OS Type
            IP Address
            Location
            User domain
            Department
            Tuning Parameters
            HA Set ID
        
        
        Port Attributes
        
            Node and Port Name
            Supported Protocols
            Class of Service
            Vendor
            Location
            User domain
            Tuning Parameters
        
        
        Paths Attributes
        
            Transfer rate capabilities
            Latency
            Redundancy
            Tuning Parameters
            Total Connectivity Units
            Connectivity Unit Information
        
        
        Internal Device Attributes
        
            VSX
            
                Name
                Location
                HA Set ID
                Cluster capabilities
                Cascading capabilities
                Tuning Parameters
            
            
        
        
        Switch Attributes
        
            Vendor
            Supported Protocols
            Domains
            Number of Ports
            Number of Connected Nodes
            Node Information
            Connected Node Information
            Location
            User domain
            HA Set ID
            Tuning Parameters
            Security capabilities
            WWN
        
        
        HUB Attributes
        
            Vendor
            Supported Protocols
            Number of Ports
            Number of Connected Nodes
            Node Information
            Connected Node Information
            Location
            User domain
            HA Set ID
            Tuning Parameters
            Security capabilities
            WWN
        
        
        Bridge Attributes
        
            Vendor
            Supported Protocols
            Number of buses
            Number of connected physical LUNs
            Location
            User domain
            HA Set ID
            Tuning Parameters
            Security capabilities
            WWN

Discovery Process

        
        
    
    


Referring to FIG. 4, a high level data flow diagram shows the flow of data during Discovery processing in accordance with an embodiment of the invention. The Discovery Manager process 402 issues a request to each Basic Discovery process 404 to report on its devices. In turn, the Basic Discovery process will issue a request to one or more Discovery Agent process 408 to report on its devices. Each Discovery Agent will probe the external network and send the device information to Basic Discovery as it's being discovered. Basic Discovery will announce each discovered element to its respective Discovered Object Managers 420 which in turn will perform device bring-up and initialization. This process will continue until Basic Discovery is done for all external devices. Basic Discovery will verify support for each device before announcing each supported device type to its Device Manager. In addition, each Discovered Object Manager will also verify support within its particular device. Once support is verified, additional device initialization is then performed by the Discovered Object Managers.
Each Discovered Object Manager 420 implements the device-specific discovery, characterization, and profiling. For each qualified device, a table of bring-up, characterization, and profiling parameters is consulted for the command group and operation code required to perform the specific discovery, characterization, or profiling procedure. The bring-up group will contain the codes for initializing the device. The programming group will contain the codes for programming the logical unit's mode pages. A group for failover processing will contain the codes for failover. The Discovery Service will dynamically generate the sequencer for the function by using the parameters for the device from the table. The command codes are not SCSI operation codes but are internal operation codes that associate with handlers that perform the corresponding operation. For example, it could be a SCSI operation or some operation to program the logical unit.
FIG. 5 is a data flow diagram showing the flow of information from various Discovered Object Managers 510 to a Media Abstraction Manager 504 and a Host Abstraction Manager 502. The figure shows typical Discovered Object Managers such as a Common Host Path Manager 511, a Native Device Manager 512, a Direct Access Device Manager 513, a RAID Device Manager 514, and a Common Device Path Manager 515. Media and Host Abstraction Layer Announcements will be conditional for all multi-ported devices based on Failover for high availability.
Paths that connect an Initiator Port to an SP Port are mapped to HBA objects. These HBAs are then mapped to Host objects. The creation of Host objects will be a manual process. The mapping of HBAs to these Hosts will be an automatic process. The HBA, Host, and Path information will be made available to create Host LUNs.
Paths that connect a Target Port to one SP Port are combined into various SCSI target devices and are grouped according to the SCSI standard. For RAID controllers pretending to be Direct Access Devices, identifying the storage as RAID will be a manual process.
All discovered objects are subject to support. Each supported external device will have a Device Characteristics Profile, from which the Device Manager can group devices within type. This requires manual setup at the factory. Initially, two simple classifications can be maintained:

    
    
        RAID should be separated from DISK storage devices
        Single ported downstream storage devices should be separated from multi-ported storage devices.

Classifications should be easily added in the form, “Property=Value”; e.g., Performance=10.

    
    


Once the Host Manager 502 and the Media Manager 504 match the Discovered Physical Devices with the Configured Virtual Devices, the Virtual Devices need to be given back to the SPs so the VSX can do 10. FIGS. 5 and 6 show the data flow diagrams for configuring storage on the SPs. The Virtual LUN Manager 506 receives information relating to the configured virtual devices (FIG. 5) and distributes configuration parameters to each SP in the VSX (FIG. 6). A storage configuration agent 602 running on the SP manages adding and removing tables and data structures.
When all SPs and Object Managers are done, Basic Discovery will send its reply back to the Discovery Manager. The Discovery Manager will wait until Basic Discovery is done on all VSX cards before announcing the external objects to the Host and Media Managers. The Path Managers will analyze each initiator and target device for additional paths. When done the Physical LUN information can be announced to the LUN Service. At this stage, Discovery is complete.
FIG. 7 shows an Administrator 702 assigning a storage device to a user domain. For example, the figure shows the Administrator communicating assignment information 712 to the Discovery Manager 704 relating to SAN elements for user domains. An Access Control Manager 706 manages user domains and user accounts within the user domains, including defining user domains, their users, access privileges and so on. The Access Control Manager informs the Discovery Manager of the different user domains. For example, Discovery Manager stores information relating to an “accounting” user domain 714 and information relating to an “R&D” user domain 716 in respective data stores 722 and 724. After the assignment is made, only the administrator or the assigned user group can view the device.
In accordance with the embodiment of the present invention, a discovered physical device can be associated with one or more virtual devices (VLUN). Moreover, each PLUN can be associated with one or more virtual devices. Furthermore, a physical device can have two or more associated PLUNs. Such assignments are handled by the Virtual LUN Manager 506. From this, it can be seen that a physical device can be assigned to more than one user domain. The higher-level storage abstractions created from the device inherit the same user domain. In this way users will see only those devices to which they have been granted access by the administrator, establishing a “Virtual” data center for each user domain.
The user can configure the Discovery Manager to periodically take an inventory of a SAN's physical topology. The user can then generate reports that show the differences between two baselines. This capability enables the user to better plan a data center's growth.
When instructed by the user, or from a user-based policy, the Discovery Service obtains a baseline inventory of all SAN elements in the SAN. Should the policy request, the Discovery Service will compare the new baseline to the existing baseline and report the differences between baselines. Later, Discovery could use a known baseline by which devices could be found. Discovery Performance can be improved by providing search parameters to the Discovery Manager. For example, a list of subnets to search could be provided as a parameter.
FIG. 8 shows the sequence of commands and events that occur during the Discovery Process for adding a single new SCSI device. FIG. 9 shows the sequence of commands and events that occur when a SCSI device is removed.
Discovery Manager Responsibilities
The Discovery Manager coordinates Discovery Service operations between the VSCs, Discovered Object Managers, and Basic Discovery. The Discovery Manager will consolidate all Basic Discovery information into one database. The Discovery Manager will send out a Report Devices command to all Basic Discovery Engines. When all the responses return, the Discovery Manager will have a complete picture of the devices attached to the VSX.
Failover will instruct the Discovery Managers which mode to use when announcing the external hosts and devices to the Discovered Object Managers for further bring-up processing and abstraction. There are two levels of announcements, Device Level announcements, and Media Level Announcements.
Device Level announcements instruct the Device Managers to perform all additional bring-up on the device, but not to make the media available to the Media Layer. Media level announcements instruct each Device Manager to bring up the device and inform the Media layer of new devices found. Only dual ported devices are subject to device level announcements.
The Discovered Object Managers on the Master VSC will do media level announcements of discovered devices. The Discovered Object Manager on the Slave VSC will do device level announcements only. That way, if there's a VSC failover, all the Slave Discovered Object Manager has to do is announce the media to the Media Layer.
In a VSX cluster, both Discovered Object Managers in either VSC will do device level announcements only. After determining device ownership, Failover will instruct the Device Manager which devices require media level announcement.
Basic Discovery Responsibilities
Basic Discovery coordinates Discovery Service operations between the Discovery Agents running on the SPs. When Basic Discovery is started, it remains dormant until a Report Devices message is received. At that time, it will query each of the Network Processors on its card for their discovery data. Discovery Agent events will be passed on to the Discovered Object Managers for processing. A reply to the Report Devices message will be sent after the database has been completely updated. Basic Discovery is also responsible for passing along topology changes to Discovery Managers as well as Discovery Object Managers.
Discovery Agent Responsibilities
Discovery Agents will initiate discovery as part of the functional code at initialization time and at run time. When the Agent receives the Report Devices command it will cause the FC Manager to probe the SAN.
Initiator SP Ports will perform initiator based discovery operations. Target SP Ports will perform target based discovery operations. Initiator and Target SP Ports will perform both initiator and target based discovery operations. What discovery operations are performed will depend on the SCSI role and the fibre channel topology. FCAL, Point-to-Point, and Fabric all support different discovery mechanisms. FCAL discovery will cause Loop Initialization (LIP). Fabric discovery will use the Fabric Name Server. Port Login and Process Login are common to all FC topologies. The higher layer software will flag conflicts such as an initiator discovering another initiator.
For each unknown discovered device the SP will create the following data structures:

    
    
        For each target device discovered by an initiator do
        
            Create a pDevPath and a pLUN for target LUN 0. The pLUN attributes should include:
            
                Peripheral Device Type set to UNKNOWN
                LUN set to 0
                Path Count set to 1
                Handle
            
            
            Generate a SAN Element Report
        
        
        For each initiator device discovered by a target do:
        
            Create a pDevPath and a generic hLUN. The hLUN should be used for requests to all supported logical unit numbers. The hLUN attributes should include:
            
                Unit Attention Set to Power On Reset
                Access set to READ/WRITE
                ASC and ASCQ set to NOT READY, BECOMING READY
                Peripheral Device Type set to UNKNOWN
                Peripheral Qualifier set to CONNECTED
                Handle
            
            
            Generate a SAN Element Report
            New commands for any generic hLUN received from an initiator should respond with CHECK CONDITION, NOT READY, BECOMING READY
        
        
    
    


After the discovery process ends, the SP will have a structure for each initiator and target port (portCB), and each target logical unit (pLUN and hLUN). The Discovery Agent will assign the handle for each discovered object. The handle will be used to identify the device when performing a device operation.
The SP will retain these structures and behavior until receiving a Configure SP command. The SP will initiate discovery in the VSC in the same way as on the line card. A Report Devices command response will be sent to Basic Discovery when the SP is done.
The Discovery Agent is responsible for reporting all network specific information and generic device information.
Discovered Object Manager Responsibilities
Discovered Object Managers are responsible for initializing the discovered device, if necessary, and making the device ready for other services. They also provide a client interface that is device-specific. Following is a description of the SCSI Device Object Manager. The device management state machine is shown in FIG. 10. The discussion of the SCSI Device Object Manager is an example of a Discovered Object Manager, illustrating the typical functions provided by a Discovered Object Manager. It is understood that similar manager processes are needed for device types other than SCSI devices.
SCSI Device Manager
Storage Devices encompass a variety of existing and future types of devices that provide the capability of storing information permanently onto Physical Volumes. Types of storage devices are distinguished by their interface characteristics that generally determine their management behavior.
SCSI Storage Devices are an example of such storage devices, having a SCSI type of interface and responding to well-known SCSI protocols. The SCSI Device Manager is concerned only with SCSI type Storage Devices. No form of SCSI is excluded from what the SCSI Device Manager is required to manage (i.e., SCSI-1, SCSI-2, etc.). Other types of Storage Devices will require implementation of other device managers, as exemplified by the SCSI Storage Devices.
a. Storage Device Management
The SCSI Device Manager is required to provide the following storage device management functions:

    
    
        The SCSI Device Manager manages the database of descriptions of SCSI devices. This includes creation of database entries when devices are first recognized, modification when state changes occur on the device, and removal of entries when devices no longer exist.
        The SCSI Device Manager is required to respond to notification from Discovery regarding the current status of the storage devices.
        The SCSI Device Manager must be able to perform all required functions on any type of SCSI device. Only the SCSI Device Manager should need changes for VSX to support new types of SCSI devices.
        The SCSI Device Manager defines the failure modes and error recovery mechanisms for all SCSI device types. This provides a centralized database for all types of failures for such a device cross-matched with the error recovery mechanism for the defined failure mode. This information is provided to the Fault Management subsystem to provide full fault management of SCSI devices.
    
    


b. Storage Device Initialization
The SCSI Device Manager manages bring-up of the SCSI devices. In this role, the SCSI Device Manager is responsible for determining the initial state of the devices when it is presented to it by the Discovery Manager. It must then perform whatever action is necessary to take to bring the device to a state of readiness so other services can use it. The Bring-up state machine is shown in FIG. 11.
Each logical unit should be brought up using the state machine in FIG. 11. This state machine could be easily modified to support RAID Controllers and Report LUNs.
c. Client Interface
The SCSI Device Manager provides registration services for clients who wish to be informed when SCSI devices come into and go out of the system. This includes providing notification services to registered clients for changes that occur on devices such as failures, readiness, etc.
The SCSI Device Manager also provides an ownership scheme whereby clients can reserve a SCSI device for exclusive access. Other clients will not be informed of the device's existence when another client has exclusive access to the device.
The SCSI Device Manager provides standard interfaces to clients for common services provided by all device managers. The SCSI Device Manager provides translation services for all native device requests addressed to a device. The SCSI Device Manager accepts requests from clients. All IO requires client-supplied buffers.
HBA Manager
Host Bus Adapters, or HBAs, encompass a variety of existing and future types of devices that provide the capability of interfacing a Server to the SAN infrastructure. The HBA management state machine is shown in FIG. 12. Types of HBAs are distinguished by their interface characteristics that generally determine their management behavior.
Fibre Channel HBAs are those HBAs that have a fibre channel type of interface and respond to fibre channel protocols. The FC HBA Manager is concerned only with fibre channel type HBAs. The IP HBA Manager is concerned only with IP type HBAs.
a. HBA Management
The HBA Manager is required to provide the following device management functions:

    
    
        The HBA Manager manages the database of descriptions of HBA devices. This includes creation of database entries when devices are first recognized, modification when state changes occur on the device, and removal of entries when devices no longer exist.
        The HBA Manager is required to respond to notification from Discovery regarding the current status of the HBAs.
        The HBA Manager must be able to perform all required functions on any type of HBA device. Only the HBA Manager should need changes for VSX to support new types of HBAs.
        The HBA Manager defines the failure modes and error recovery mechanisms for all HBA types. This provides a centralized database for all types of failures for such a device cross-matched with the error recovery mechanism for the defined failure mode. This information is provided to the Fault Management subsystem to provide full fault management of HBA devices.
    
    


b. HBA Initialization
The HBA Manager manages bring-up of the HBA devices. In this role, the HBA Manager prepares the HBA for abstraction. There are currently no special operations to perform on an HBA for bring-up.
c. Client Interface
The HBA Manager provides registration services for clients who wish to be informed when an HBA comes into and goes out of the system.
The HBA Manager provides notification services to registered clients for changes that occur on HBAs. These include failures, removals, etc.
The HBA Manager provides standard interfaces to clients for common services provided by all device managers such as Vendor retrieval.
Path Manager
The Path Manager identifies routing and pathing choices from the Server to its storage. The path management state machine is shown in FIG. 13. A Path is a logical connection in the SAN infrastructure used for data transfer between a Server and the VSX, or between the VSX and a Storage Element. As such, there are two distinct path types, Server Paths and Storage Paths. Server paths provide the capability of transferring data between computer systems (Servers) and the VSX. Storage paths provide the capability of transferring information between storage elements and the VSX.
a. Path Management
The Path Manager is required to provide the following path management functions:

    
    
        The Path Manager manages the database of Path descriptions. This includes creation of database entries when paths are first recognized, modification when state changes occur on the path, and removal of entries when paths no longer exist.
        The Path Manager is required to respond to notification from Discovery regarding the current status of a path.
        The Path Manager must be able to perform all required functions on any type of path. Only the Path Manager should need changes for VSX to support new types of Paths; e.g., Path from one VSX to another VSX.
        The Path Manager defines the failure modes and error recovery mechanisms for all path types. This provides a centralized database for all types of failures for paths cross-matched with the error recovery mechanism for the defined failure mode. This information is provided to the Fault Management subsystem to provide full fault management of paths.
    
    


b. Path Initialization
The Path Manager does not participate in path initialization. It is the device-specific manager that determines path initialization as a byproduct of the device bring-up. In this role, the Path Manager is responsible for determining multiple access paths of a device when it is presented to it by the Discovery Manager. It must then analyze the path data in order to bring the HBAs or storage elements to a state of readiness so the abstraction layer can use it.
c. Client Interface
The Path Manager provides registration services for clients who wish to be informed when Paths come into and go out of the system.
The Path Manager provides notification services to registered clients for changes that occur on paths. These include failures, readiness, etc.
The Path Manager provides standard interfaces to clients for common services provided by all device managers.
Managing Topology Changes
There will be topology changes that occur asynchronously from the SPs. The network itself can change through the addition or removal of a device in the network. These will cause the database to be updated and changes propagated back to the Device Managers as needed without the need for Report Devices.
Only changes will be reported. The Discovery Agent will report changes to Basic Discovery. Basic Discovery will report changes to the Object Managers and to the Discovery Manager. The Object Managers will propagate changes to the LUN services for media announced devices. An Add or Remove operation for a device level announcement would not affect the media layer but would be announced to clients requesting this notification. Changes will be expressed as additions or subtractions.
Device removals are detected in several ways. The IO path can detect the device being removed through command time outs. The Fibre Channel layer can detect the device being removed through Loop Initialization Processing or a switch Name Server. An SES Manager can detect a device being removed using the SES protocol. When notified of device removals the SP will abort all outstanding IO to the device, reroute the IO if programmed to, and remove the associated data structures.
Additions can be detected through SES or the SP. Any additions such as a new host login will cause discovery to be restarted on that SP. New upstream or downstream devices will cause the SP to again create default LUN structures to handle IO requests. IO to existing devices will be unaffected.
Managing Discovery on Demand
After the VSX is operational, the user can invoke Report Devices to the Discovery Manager at any time to refresh the information in the Database. Report Devices can be invoked on the VSX as a whole, on a particular card, or on a particular SP. Only one Report Devices command is active at any one time on each SP. If a Report Devices comes in during Report Devices processing, the response is held off until the process is complete. Again, only changes will be reported. Re-discovery will not impact 10 operations.
Discovery Operations


    
    
        Initialize—Initialize instructs the Discovery Service to perform subsystem initialization.
        Enable—Enable instructs the Discovery Service to activate the subsystem for command and event processing.
        Disable—Disable instructs the Discovery Service to quiescence for shutdown.
        Report Devices—Report Devices instructs the Discovery Service to re-scan all or some of the VSX interfaces for attached devices and report back when done. The Topology Data returned from the scan operation is saved in the Database. Some or all of the topology is announced to the caller.
        Create Baseline—Create Baseline instructs the Discovery Manager to save the live configuration into a baseline.
        Report Baseline Changes—Report Baseline Changes queries the Discovery Manager for the difference between the baseline configuration and the live configuration.
        Report Network Performance—Report Network Performance instructs Discovery to discover the performance characteristics of the network.
        Report Failed SAN Elements—Report Failed SAN Elements instructs Discovery to retrieve all the SAN elements whose status is failed.
        SAN Element Report—SAN Element Report is an event that notifies the Discovery Service that the external port topology has changed. The SP is the source of the event. There are four different types of event reports.

Discovery Service Context

    
    


Other software that uses this service includes:

    
    
        User Interface (CLI or GUI)—The User Interface uses Discovery Services to enable the customer to visualize the SAN to achieve a number of tasks, such as hardware connectivity.
        SNMP—SNMP uses Discovery Services to identify the VSX itself, manage reporting faults and for certain storage configuration.
        Storage Allocation—Storage Allocation uses Discovery Services to differentiate between types of storage being used for allocation.
        Storage Access and Security—LUN Masking uses Discovery Services to identify Hosts and HBAs.
        Inventory and Asset Management—Inventory and Asset Management use Discovery Services to help determine the correct allocation of network resources.
        Capacity Planning—Capacity Planning uses Discovery Services to determine and report on the capacity of various pools of storage
        LUN Service—PLUN Object Managers provide PLUN to the LUN service for abstraction
        Host Service—HBA Object Managers provide HBAs to the Host Service for Server abstraction.
    
    


Other software this service uses includes:

    
    
        Failover—Failover identifies to Discovery Services which devices get media announcements
        Chassis Service—Chassis Service provides the SP port, Line Card, Virtual Storage Controller, and other hardware objects
        VSX Configuration—Provides events that cause auto-discovery: LC changed, Port changed
        System Software—System Software provides infrastructure specific probing and topology change management to Discovery Services
    
    


The invention provides an automated method for discovering and classifying information about a fibre channel device in a network that significantly improves the widely used manual method of discovery and classification. Specifically, the invention provides a method for determining a storage device's reliability, availability, failover policy, command support, access time and throughput automatically. To accomplish the fibre channel device discovery and classification, standard SCSI commands are sent to the storage device.
The invention provides an important technical advantage by discovering a device's reliability by distinguishing RAID versus non-RAID storage devices using the SCSI Inquiry command. For example, a RAID logical unit's reliability rating is higher than a physical disk logical unit's reliability rating.
The present invention provides another technical advantage by discovering a fibre channel storage device in a storage area network that is highly available using the multi-port indicator and device identifier vital product data page.
The invention provides another technical advantage related to multi-pathing by discovering a device's multi-port failover behavior using standard SCSI commands. Multiple read requests are sent to both device ports simultaneously. If both ports can sustain command, data, and status transfers the device is classified as Active-Active. If only one port can be used at a time, the device is classified as Active-Passive. Such multi-path behavior can be matched to a computer system's multi-path behavior automatically, without the user having to guess.
The invention provides another technical advantage related to command compatibility between storage devices and servers by discovering a storage device's command support. Requests are sent to the storage device to inquire whether the command is supported or not. Unsupported commands can be emulated in the VSX. The command set support can be matched to a computer system's command set support thereby providing compatibility between two entities that would otherwise be incompatible.
The invention also provides another technical advantage by discovering the access time of a fibre channel storage device in a storage area network by issuing block level I/O requests and measuring the time it takes the device to return the first byte of data.
The invention also provides another technical advantage by discovering the data rate of a fibre channel storage device in a storage area network by issuing block level requests and measuring the amount of data transferred per unit time.
The invention also provides another technical advantage by grouping devices into classifications by attributes for application software. Applications can then satisfy storage requests based on device characteristics.
The invention also provides a technical advantage by providing a scheme that allows device support to be specified and added very easily and in some cases without code recompilation. The general idea is to create a table of device bring-up parameters for each qualified device. This table of parameters will essentially contain the command group type and command operation code for each behavior that needs to be executed for the storage device. The codes map to internal VSX state machine sequencers. The behaviors supported are device bring-up, failover, and other in-band management functions, such as LUN configuration.
The invention also provides a technical advantage facilitating global storage management and security by providing the user the capability of assigning a SAN device to a user domain. Only users granted permission to that domain could view network topology and status information.
The invention also provides a means to measure and predict the growth of a data center by automating the creation and comparisons of inventory baselines using policy management. The user can configure the discovery manager to run periodic inventory reports facilitating data center planning.

## Claims

1. A storage management device for exchanging data between a plurality of computers that are external to the storage management device and a plurality of storage devices that are external to the storage management device, the storage management device comprising:
one or more control modules, each having one or more first data ports;
one or more storage control modules, each having one or more second data ports;
one or more data stores;
a switch fabric configured to selectively exchange data among said first data ports and said second data ports, some of said first data ports and said second data ports to communicate data with said computers that are external to the storage management device, others of said first data ports and said second data ports to communicate data with said storage devices that are external to the storage management device;
first program code adapted to execute on each of said one or more control modules, and
second program code adapted to execute on each of said one or more storage control modules,
said first program code comprising:
a first code component configured to operate one of said control modules to issue a request for device information;
a second code component configured to operate one of said storage control modules to receive said request for device information and in response thereto to obtain device information corresponding to one or more of said one or more storage devices, said device information being stored in said one or more data stores; and
a third code component configured to operate one of said control modules to receive said device information and in response thereto to initialize, characterize, and profile said corresponding storage devices.

2. The device of claim 1 wherein said one or more storage control modules each includes a plurality of storage processing units, each of said storage processing units comprising one or more of said second ports, said second code component comprises:
a first code portion configured to operate one of said storage control modules to receive said request for device information and in response thereto to communicate said request to each storage processing unit; and
a second code portion configured to operate one of said storage processing units to receive said request and in response thereto to communicate via said one or more of said second ports to obtain said device information.

3. The device of claim 1 wherein said second code component is further configured to operate one of said storage control modules to obtain path information, said path information identifying data paths between said second data ports and said storage devices, said path information being stored in said one or more data stores.

4. The device of claim 3 wherein said second code component is further configured to operate one of said storage control modules to detect changes in said path information, said changes in said path information being stored in said one or more data stores.

5. The device of claim 1 wherein said second code component is further configured to operate one of said storage control modules to detect addition of a storage device.

6. The device of claim 5 wherein said second code component is further configured to operate one of said storage control modules to detect addition of a storage device.

7. The device of claim 1 wherein said second code component is further configured to operate one of said storage control modules to detect addition of one or more data coupling devices, said data coupling devices effective for providing a data communication between some of said first and second data ports and some of said storage devices.

8. The device of claim 7 wherein said second code component is further configured to operate one of said storage control modules to detect deletion of one or more of said coupling devices.

9. The device of claim 1 wherein said device information includes one or more of reliability information, availability information, a failover policy, command support capability, and performance information.

10. The device of claim 1 further including a fourth code component configured to operate one of said control modules to receive user-provided information relating to a configuration of virtual storage devices and to associate said storage devices to said virtual storage devices based on said device information, wherein each device can be associated with one or more of said virtual devices, wherein each virtual device can be associated with one or more of said devices.

11. A method implemented in a storage management device for exchanging data between a plurality of computers that are external to said storage management device and a plurality of physical storage devices that are external to said storage management device, the storage management device comprising a plurality of first data ports configured for communication with said computers, a plurality of second data ports configured for communication with said physical storage devices, and a switch fabric configured to selectively exchange data among said first data ports and said second data ports, the method comprising:
communicating a request for device information;
obtaining device information corresponding to said physical storage devices that pre external to said storage management device;
based on said device information, initializing said corresponding physical storage devices;
identifying a plurality of first communication paths between said storage management device and said physical storage devices;
storing in one or more data stores said device information and path information indicative of said first communication paths;
receiving user-provided information relating to virtual storage configuration; and
based on said device information, said user-provided information and said path information, associating one or more of said physical storage devices to said virtual storage configuration.

12. The method of claim 11 wherein said device information includes one or more of reliability information, availability information, a failover policy, command support capability, and performance information.

13. The method of claim 11 further including detecting changes in said first communication paths and storing information indicative of said changes in said first communication paths in said one or more data stores.

14. The method of claim 11 further including detecting addition of a new physical storage device to said physical storage devices and removal of one of said physical storage devices and storing said addition in said one or more data stores.

15. The method of claim 11 further including detecting addition of a first data coupling device for coupling said storage management device to one or more of said physical storage devices and removal of a second data coupling device and storing said removal in said one or more data stores.

16. The method of claim 11 further including receiving user-provided information relating to a configuration of virtual storage devices; and associating said physical storage devices to said virtual storage devices based on said device information and said first communication paths, wherein each physical device can be associated with one or more of said virtual devices, wherein each virtual device can be associated with one or more of said physical devices.

17. A storage management device for exchanging data between a plurality of computers that are external to said storage management device and a plurality of physical storage devices that are external to said storage management device, the storage management device comprising:
a plurality of first data ports configured for communication with said computers that are external to said storage management device;
a plurality of second data ports configured for communication with said physical storage devices that are external to said storage management device;
a switch fabric configured to selectively exchange data among said first data ports and said second data ports;
one or more data stores;
means for communicating a request for device information;
means for obtaining device information corresponding to said physical storage devices and for storing said device information in said one or more data stores;
means for characterizing and profiling said physical storage devices based on said device information;
means for initializing said corresponding physical storage devices based on said device information;
means for identifying a plurality of first communication paths between said storage management device and said physical storage devices and for storing information indicative of said first communication paths in said one or more data stores; and
means for automatically detecting and characterizing changes in a topology of said physical storage devices and for storing said changes.

18. The device of claim 17 further including means for receiving user-provided Information relating to a configuration of virtual storage devices; and means for associating said physical storage devices to said virtual storage devices based on said device information and said path information, wherein each physical device can be associated with one or more of said virtual devices, wherein each virtual device can be associated with one or more of said physical devices.

19. The device of claim 17 wherein said changes in topology of said physical storage devices includes addition of one or more new physical storage devices and removal of one or more of said physical storage devices.

20. The device of claim 17 wherein said device information includes one or more of reliability information, availability information, a failover policy, command support capability, and performance information.

21. A storage management device for use on a storage network, the storage management device comprising:
one or more control modules, each having one or more first data ports;
one or more storage control modules, each having one or more second data ports;
a switch fabric to selectively exchange data among said first data ports and said second data ports, some of said first data ports and said second data ports to communicate data with a plurality of computers that are external to the storage management device, others of said first data ports and said second data ports to communicate data with a plurality of storage devices that are external to the storage management device;
logic to obtain device information corresponding to one or more of said one or more storage devices, wherein said device information includes reliability information, availability information, a failover policy, command support capability, and performance information; and
logic to receive said device information and in response thereto to initialize, characterize, and profile said corresponding storage devices.

22. The storage management device of claim 21, wherein said reliability information comprises information indicating whether a storage device is a RAID device or a non-RAID device.

23. The method of claim 12, wherein said device said device information includes reliability information, availability information, a failover policy, command support capability, and performance information.

24. The storage management device of claim 20, wherein said device said device information includes reliability information, availability information, a failover policy, command support capability, and performance information.

25. The storage management device of claim 20, wherein said device said device information includes reliability information, availability information, a failover policy, command support capability, and performance information.