`L.L.P.
`1600 SAN JACINTO CENTER
`98 SAN JACINTO BLVD.
`AUSTIN, TEXAS 78701-4039
`
`TELEPHONE : 151 21 322-2500
`FACSIM ILE : <512l 322-2501
`
`E-MAIL ADDRESS :
`
`WILLIAM HULSEY@BAKERBOTTS.COM
`
`December 31, 1 997
`
`DALLAS
`HOUSTON
`MOSCOW
`NEW YORK
`WASHINGTON. D .C.
`
`WILLIAM N. HULSEY Ill
`(512) 322-2548
`
`Mr. Dale Quisenberry
`Vice President of Finance
`CROSSROADS SYSTEMS, INC.
`9390 Research Blvd.
`Suite 11-300
`Austin, Texas 78759
`
`Re:
`
`Patent Application Entitled "Storage Router and Method for Providing
`Virtual Local Storage"
`Our File No. 064113.0103
`
`Dear Mr. Quisenberry:
`
`To update your file, enclosed is a copy of the draft application forwarded to Geoff
`Hoese on December 19 and a copy of the letter sent to Brian Smith on that same date. A copy of the
`application as filed is also enclosed.
`
`The application should be accorded a filing date of December 31, 1997, by the U.S.
`Patent and Trademark Office because the application was mailed on that date by the U.S. Postal
`Service's Express Mail service. By copy of this letter, we are sending a copy of the filed application
`to the inventors.
`
`Should have any questions or comments, please do not hesitate to call me at ( 512)
`
`322-2548.
`
`Very truly yours,
`
`BAKER & BOTTS, L.L.P.
`
`L.
`
`WNH/rmf
`Enclosures
`cc: Mr. Geoffrey B. Hoese - w/Encl.
`Mr. Jeffry T. Russell - w/Encl.
`
`AUSOl:l25096.I
`
`~~~
`J
`
`William N. Hulsey III
`
`Confidential I
`Attorneys' Eyes Only
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`1 of 33
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`·-.:-·- ·.-..... ...
`...... ; 0 ·' "
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`LJ tJ
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`-···" --
` CROSSROADS EXHIBIT 2323
`Oracle Corp., et al v. Crossroads Systems, Inc.
` IPR2014-01207 and IPR2014-1209
`
`. •
`
`CROSSROADS EXHIBIT
`Oracle Corp. v. Crossroads Systems, Inc.
`IPR2015-0(cid:1005)(cid:1004)(cid:1010)(cid:1008)
`
`2323
`
`
`
`t ·\" .
`..
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`ATTORNEYS DOCKET
`064113.0103
`
`PATENT APPLICATION
`
`1
`
`STORAGE ROUTER AND METHOD FOR
`
`PROVIDING VIRTUAL LOCAL STORAGE
`
`TECHNICAL FIELD OF THE INVENTION
`
`This invention relates in general to network storage
`
`devices, and more particularly to a storage router and
`
`method for providing virtual local storage on remote SCSI
`
`5
`
`storage devices to Fibre Channel devices.
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`BACKGROUND OF THE INYENTION
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`2
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`PATENT APPLICATION
`
`Typical storage transport mediums provide for a
`
`relatively small number of devices to be attached over
`
`relatively short distances. One such transport medium is
`
`5
`
`a Small Computer System Interface (SCSI) protocol, the
`
`structure and operation of which is generally well known
`
`as is described, for example, in the SCSI-1, SCSI-2 and
`
`SCSI-3 specifications. High speed serial interconnects
`
`provide enhanced capability to attach a large number of
`
`10
`
`high speed devices to a common storage transport medium
`
`over large distances. One such serial interconnect is
`
`Fibre Channel, the structure and operation of which is
`
`described, for example, in Fibre Channel Physical and
`
`Signaling Interface (FC-PH), ANSI X3.230 Fibre Channel
`
`15
`
`Arbitrated Loop (FC-AL), and ANSI X3.272 Fibre Channel
`
`Private Loop Direct Attach (FC-PLDA).
`
`Conventional computing devices, such as computer
`
`workstations, generally access storage locally or through
`
`network interconnects. Local storage typically consists
`
`20
`
`of a disk drive, tape drive, CD-ROM drive or other
`
`storage device contained within, or locally connected to
`
`the workstation. The workstation provides a file system
`
`structure, that includes security controls, with access
`
`to the local storage device through native low level,
`
`25
`
`block protocols. These protocols map directly to the
`
`mechanisms used by the storage device and consist of data
`
`requests without security controls. Network interconnects
`
`typically provide access for a large number of computing
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`3
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`devices to data storage on a remote network server. The
`
`remote network server provides file system structure,
`
`access control, and other miscellaneous capabilities that
`
`include the network interface. Access to data through
`
`5
`
`the network server is through network protocols that the
`
`server must translate into low level requests to the
`
`storage device. A workstation with access to the server
`
`storage must translate its file system protocols into
`
`network protocols that are used to communicate with the
`
`~ .
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`10
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`server. Consequently, from the perspective of a
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`workstation, or other computing device, seeking to access
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`such server data, the access is much slower than access
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`to data on a local storage device.
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`SPMMARY OF THE INYENTION
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`4
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`PATENT APPLICATION
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`In accordance with the present invention, a storage
`
`router and method for providing virtual local storage on
`
`remote SCSI storage devices to Fibre Channel devices are
`
`5
`
`disclosed that provide advantages over conventional
`
`network storage devices and methods.
`
`According to one aspect of the present invention, a
`
`storage router and storage network provide virtual local
`
`storage on remote SCSI storage devices to Fibre Channel
`
`10
`
`devices. A plurality of Fibre Channel devices, such as
`
`workstations, are connected to a Fibre Channel transport
`
`medium, and a plurality of SCSI storage devices are
`
`connected to a SCSI bus transport medium. The storage
`
`router interfaces between the Fibre Channel transport
`
`15
`
`medium and the SCSI bus transport medium. The storage
`
`router maps between the workstations and the SCSI storage
`
`devices and implements access controls for storage space
`
`on the SCSI storage devices. The storage router then
`
`allows access from the workstations to the SCSI storage
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`20
`
`devices using native low level, block protocol in
`
`accordance with the mapping and the access controls.
`
`According to another aspect of the present
`
`invention, virtual local storage on remote SCSI storage
`
`devices is provided to Fibre Channel devices. A Fibre
`
`25
`
`Channel transport medium and a SCSI bus transport medium
`
`are interfaced with. A configuration is maintained for
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`SCSI storage devices connected to the SCSI bus transport
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`medium. The configuration maps between Fibre Channel
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`devices and the SCSI storage devices and implements
`
`access controls for storage space on the SCSI storage
`
`devices. Access is then allowed from Fibre Channel
`
`initiator devices to SCSI storage devices using native
`
`5
`
`low level, block protocol in accordance with the
`
`configuration.
`
`A technical advantage of the present invention is
`
`the ability to centralize local storage for networked
`
`workstations without any cost of speed or overhead. Each
`
`10
`
`workstation access its virtual local storage as if it
`
`work locally connected. Further, the centralized storage
`
`devices can be located in a significantly remote position
`
`even in excess of ten kilometers as defined by Fibre
`
`Channel standards.
`
`15
`
`Another technical advantage of the present invention
`
`is the ability to centrally control and administer
`
`storage space for connected users without limiting the
`
`speed with which the users can access local data.
`
`In
`
`addition, global access to data, backups, virus scanning
`
`20
`
`and redundancy can be more easily accomplished by
`
`centrally located storage devices.
`
`A further technical advantage of the present
`
`invention is providing support for SCSI storage devices
`
`as local storage for Fibre Channel hosts.
`
`In addition,
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`25
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`the present invention helps to provide extended
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`capabilities for Fibre Channel and for management of
`
`storage subsystems.
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`PATENT APPLICATION
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`BRIEF DESCRIPTION OF THE DRAWINGS
`
`A more complete understanding of the present
`
`invention and the advantages thereof may be acquired by
`
`referring to the following description taken in
`
`5
`
`conjunction with the accompanying drawings, in which like
`
`reference numbers indicate like features, and wherein:
`
`FIGURE 1 is a block diagram of a conventional
`
`network that provides storage through a network server;
`
`FIGURE. 2 is a block diagram of one embodiment of a
`
`10
`
`storage network with a storage router that provides
`
`global access and routing;
`
`FIGURE 3 is a block diagram of one embodiment of a
`
`storage network with a storage router that provides
`
`virtual local storage;
`
`15
`
`FIGURE 4 is a block diagram of one embodiment of the
`
`storage router of FIGURE 3; and
`
`FIGURE 5 is a block diagram of one embodiment of
`
`data flow within the storage router of FIGURE 4.
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`DETAILED DESCRIPTION OF THE INYENTION
`
`FIGURE 1 is a block diagram of a conventional
`
`network, indicated generally at 10, that provides access
`
`to storage through a network server. As shown, network
`
`5
`
`10 includes a plurality of workstations 12 interconnected
`
`with a network server 14 via a network transport medium
`
`16. Each workstation 12 can generally comprise a
`
`processor, memory, input/output devices, storage devices
`
`and a network adapter as well as other common computer
`
`,.
`
`10
`
`components. Network server 14 uses a SCSI bus 18 as a
`
`storage transport medium to interconnect with a plurality
`
`of storage devices 20 (tape drives, disk drives, etc.).
`
`In the embodiment of FIGURE 1, network transport medium
`
`16 is an network connection and storage devices 20
`
`15
`
`comprise hard disk drives, although there are numerous
`
`alternate transport mediums and storage devices.
`
`In network 10, each workstation 12 has access to its
`
`local storage device as well as network access to data on
`
`storage devices 20. The access to a local storage device
`
`20
`
`is typically through native low level, block protocols.
`
`On the other hand, access by a workstation 12 to storage
`
`devices 20 requires the participation of network server
`
`14 which implements a file system and transfers data to
`
`workstations 12 only through high level file system
`
`25
`
`protocols. Only network server 14 communicates with
`
`storage devices 20 via native low level, block protocols .
`
`Consequently, the network access by workstations 12
`
`through network server 14 is slow with respect to their
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`access to local storage.
`
`In network 10, it can Also be a
`
`logistical problem to centrally manage and administer
`
`local data distributed across an organization, including
`
`accomplishing tasks such as backups, virus scanning and
`
`5
`
`redundancy.
`
`FIGURE 2 is a block diagram of one embodiment of a
`
`storage network, indicated generally at 30, with a
`
`storage router that provides global access and routing.
`
`This environment is significantly different from that of
`
`10
`
`FIGURE 1 in that there is no network server involved.
`
`In
`
`FIGURE 2, a Fibre Channel high speed serial transport 32
`
`interconnects a plurality of workstations 36 and storage
`
`devices 38. A SCSI bus storage transport medium
`
`interconnects workstations 40 and storage devices 42. A
`
`15
`
`storage router 44 then serves to interconnect these
`
`mediums and provide devices on either medium global,
`
`transparent access to devices on the other medium.
`
`Storage router 44 routes requests from initiator devices
`
`on one medium to target devices on the other medium and
`
`20
`
`routes data between the target and the initiator.
`
`Storage router 44 can allow initiators and targets to be
`
`on either side.
`
`In this manner, storage router 44
`
`enhances the functionality of Fibre Channel 3~ by
`
`providing access, for example, to legacy SCSI storage
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`25
`
`devices on SCSI bus 34.
`
`In the embodiment of FIGURE 2,
`
`the operation of storage router 44 can be managed by a
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`management station 46 connected to the storage router via
`
`a direct serial connection.
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`In storage network 30, any workstation 36 or
`
`workstation 40 can access any storage device 38 or
`
`storage device 42 through native low level, block
`
`protocols, and vice versa. This functionality is enabled
`
`S
`
`by storage router 44 which routes requests and data as a
`
`generic transport between Fibre Channel 32 and SCSI bus
`
`34. Storage router 44 uses tables to map devices from
`
`one medium to the other and distributes requests and data
`
`across Fibre Channel 32 and SCSI bus 34 without any
`
`10
`
`security access controls. Although this extension of the
`
`high speed serial interconnect provided by Fibre Channel
`
`32 is beneficial, it is desirable to provide security
`
`controls in addition to extended access to storage
`
`devices through a native low level, block protocol.
`
`15
`
`FIGURE 3 is a block diagram of one embodiment of a
`
`storage network, indicated generally at SO, with a
`
`storage router that provides virtual local storage.
`
`Similar to that of FIGURE 2, storage network SO includes
`
`a Fibre Channel high speed serial interconnect S2 and a
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`20
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`SCSI bus 54 bridged by a storage router S6. Storage
`
`router 56 of FIGURE 3 provides for a large number of
`
`workstations 58 to be interconnected on a common storage
`
`transport and to access common storage devices 60, 62 and
`
`64 through native low level, block protocols.
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`25
`
`According to the present invention, storage router
`
`56 has enhanced functionality to implement security
`
`controls and routing such that each workstation S8 can
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`have access to a specific subset of the overall data
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`stored in storage devices 60, 62 and 64. This specific
`
`subset of data has the appearance and characteristics of
`
`local storage and is referred to herein as virtual local
`
`storage. Storage router 56 allows the configuration and
`
`5
`
`modification of the storage allocated to each attached
`
`workstation 58 through the use of mapping tables or other
`
`mapping techniques.
`
`As shown in FIGURE 3, for example, storage device 60
`
`can be configured to provide global dat~ 65 which can be
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`10
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`accessed by all workstations 58. Storage device 62 can
`
`be configured to provide partitioned subsets 66, 68, 70
`
`and 72, where each partition is allocated to one of the
`
`workstations 58 (workstations A, B, C and D) . These
`
`subsets 66, 68, 70 and 72 can only be accessed by the
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`15
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`associated workstation 58 and appear to the associated
`
`workstation 58 as local storage accessed using native low
`
`level, block protocols. Similarly, storage device 64 can
`
`be allocated as storage for the remaining workstation 58
`
`(workstation E) .
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`20
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`Storage router 56 combines access control with
`
`routing such that each workstation 58 has controlled
`
`access to only the specified partition of storage device
`
`62 which forms virtual local storage for the workstation
`
`58. This access control allows security control for the
`
`25
`
`specified data partitions. Storage router 56 allows this
`
`allocation of storage devices 60, 62 and 64 to be managed
`
`by a management station 76. Management station 76 can
`
`connect directly to storage router 56 via a direct
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`connection or, alternately, can interface with storage
`
`router 56 through either Fibre Channel 52 or SCSI bus 54.
`
`In the latter case, management station 76 can be a
`
`workstation or other computing device with special rights
`
`5
`
`such that storage router 56 allows access to mapping
`
`tables and shows storage devices 60, 62 and 64 as they
`
`exist physically rather than as they have been allocated.
`
`The environment of FIGURE 3 extends the concept of a
`
`single workstation having locally connected storage
`
`10
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`devices to a storage network 50 in which workstations 58
`
`are provided virtual local storage in a manner
`
`transparent to workstations 58. Storage router 56
`
`provides centralized control of what each workstati9n 58
`
`sees as its local drive, as well as what data it sees as
`
`15
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`global data accessible by other workstations 58.
`
`Consequently, the storage space considered by the
`
`workstation 58 to be its local storage is actually a
`
`partition (i.e., logical storage definition) of a
`
`physically remote storage device 60, 62 or 64 connected
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`20
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`through storage router 56. This means that similar
`
`requests from workstations 58 for access to their local
`
`storage devices produce different accesses to the storage
`
`space on storage devices 60, 62 and 64. Further, no
`
`access from a workstation 58 is allowed to the virtual
`
`25
`
`local storage of another workstation 58.
`
`The collective storage provided by storage devices
`
`60, 62 and 64 can have blocks allocated by programming
`
`means within storage router 56. To accomplish this
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`function, storage router 56 can include routing tables
`
`and security controls that define storage allocation for
`
`each workstation 58. The advantages provided by
`
`implementing virtual local storage in centralized storage
`
`5
`
`devices include the ability to do collective backups and
`
`other collective administrative functions more easily.
`
`This is accomplished without limiting the performance of
`
`workstations 58 because storage access involves native
`
`low level, block protocols and does not involve the
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`10
`
`overhead of high level protocols and file systems
`
`required by network servers.
`
`FIGURE 4 is a block diagram of one embodiment of
`
`storage router 56 of FIGURE 3. Storage router 56 can
`
`comprise a Fibre Channel controller 80 that interfaces
`
`15
`
`with Fibre Channel 52 and a SCSI controller 82 that
`
`interfaces with SCSI bus 54. A buffer 84 provides memory
`
`work space and is connected to both Fibre Channel
`
`controller 80 and to SCSI controller 82. A supervisor
`
`unit 86 is connected to Fibre Channel controller 80, SCSI
`
`20
`
`controller 82 and buffer 84. Supervisor unit 86
`
`comprises a microprocessor for controlling operation of
`
`storage router 56 and to handle mapping and.security
`
`access for requests between Fibre Channel 52 and SCSI bus
`
`54.
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`25
`
`FIGURE 5 is a block diagram of one embodiment of
`
`data flow within storage router 56 of FIGURE 4. As
`
`shown, data from Fibre Channel 52 is processed by a Fibre
`
`Channel (FC) protocol unit 88 and placed in a FIFO queue
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`90. A direct memory access (DMA)
`
`interface 92 then takes
`
`data out of FIFO queue 90 and places it in buffer 84.
`
`Supervisor unit 86 processes the data in buffer 84 as
`
`represented by supervisor processing 93. This processing
`
`5
`
`involves mapping between Fibre Channel 52 and SCSI bus 54
`
`and applying access controls and routing functions. A
`
`DMA interface 94 then pulls data from buffer 84 and
`
`places it into a buffer 96. A SCSI protocol unit 98
`
`pulls data from buffer 96 and communicates the data on
`
`10
`
`SCSI bus 54. Data flow in the reverse direction, from
`
`SCSI bus 54 to Fibre Channel 52, is accomplished in a
`
`reverse manner.
`
`The storage router of the present invention is .a
`
`bridge device that connects a Fibre Channel link directly
`
`15
`
`to a SCSI bus and enables the exchange of SCSI command
`
`set information between application clients on SCSI bus
`
`devices and the Fibre Channel links. Further, the
`
`storage router applies access controls such that virtual
`
`local storage can be established in remote SCSI storage
`
`20
`
`devices for workstations on the Fibre Channel link.
`
`In
`
`one embodiment, the storage router provides a connection
`
`for Fibre Channel links running the SCSI Fibre Channel
`
`Protocol (FCP) to legacy SCSI devices attached to a SCSI
`
`bus. The Fibre Channel topology is typically an
`
`25
`
`Arbitrated Loop (FC_AL) .
`
`In part, the storage router enables a migration path
`
`to Fibre Channel based, serial SCSI networks by providing
`
`connectivity for legacy SCSI bus devices. The storage
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`router can be attached to a Fibre Channel Arbitrated Loop
`
`and a SCSI bus to support a number of SCSI devices.
`
`Using configuration settings, the storage router can make
`
`the SCSI bus devices available on the Fibre Channel
`
`5
`
`network as FCP logical units. Once the configuration is
`
`defined, operation of the storage router is transparent
`
`to application clients~ In this manner, the storage
`
`router can form an integral part of the migration to new
`
`Fibre Channel based networks while providing a means to
`
`,.
`
`10
`
`contihue using legacy SCSI devices.
`
`In one implementation (not shown), the storage
`
`router can be a rack mount or free standing device with
`
`an internal power supply. The storage router can h~ve a
`
`Fibre Channel and SCSI port, and a standard, detachable
`
`15
`
`power cord can be used, the FC connector can be a copper
`
`DB9 connector, and the SCSI connector can be a 68-pin
`
`type. Additional modular jacks can be provided for a
`
`serial port and a 802.3 lOBaseT port, i.e. twisted pair
`
`Ethernet, for management access. The SCSI port of the
`
`20
`
`storage router an support SCSI direct and sequential
`
`access target devices and can support SCSI initiators, as
`
`well. The Fibre Channel port can interface to SCSI-3 FCP
`
`enabled devices and initiators.
`
`To accomplish its functionality, one implementation
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`25
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`of the storage router uses: a Fibre Channel interface
`
`based on the HEWLETT-PACKARD TACHYON HPFC-5000 controller
`
`and a GLM media interface; an Intel 80960RP processor,
`
`incorporating independent data and program memory spaces,
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`and associated logic required to implement a stand alone
`
`processing system; and a serial port for debug and system
`
`configuration. Further, this implementation includes a
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`SCSI interface supporting Fast-20 based on the SYMBIOS
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`5
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`53CBxx series SCSI controllers, and an operating system
`
`based upon the WIND RIVERS SYSTEMS VXWORKS or IXWORKS
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`kernel, as determined by design.
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`In addition, the
`
`storage router includes software as required to control
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`basic functions of the various elements, and to provide
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`10
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`appropriate translations between the FC and SCSI
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`protocols.
`
`The storage router has various modes of operation
`
`that are possible between FC and SCSI target and
`
`initiator combinations. These modes are: FC Initiator to
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`SCSI Target; SCSI Initiator to FC Target; SCSI Initiator
`
`to SCSI Target; and FC Initiator to FC Target . The first ·
`
`two modes can be supported concurrently in a
`
`single storage router device are discussed briefly below.
`
`The third mode can involve two storage router devices
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`20
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`back to back and can serve primarily as a device to
`
`extend the physical distance beyond that possible via a
`
`direct SCSI connection. The last mode can be used to
`
`carry FC protocols encapsulated on other transmission
`
`technologies (e.g. ATM, SONET), or to act as a bridge
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`25
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`between two FC loops (e.g. as a two port fabric).
`
`The FC Initiator to SCSI Target mode provides for
`
`the basic configuration of a server using Fibre Channel
`
`to communicate with SCSI targets . This mode requires
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`that a host system have an FC attached device and
`
`associated device drivers and software to generate SCSI-3
`
`FCP requests. This system acts as an initiator using the
`
`storage router to communicate with SCSI target devices.
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`5
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`The SCSI devices supported can include SCSI-2 compliant
`
`direct or sequential access (disk or tape) devices. The
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`storage router serves to translate command and status
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`information and transfer data between SCSI-3 FCP and
`
`SCSI-2, allowing the use of standard SCSI-2 devices in a
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`10
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`Fibre Channel environment.
`
`The SCSI Initiator to FC Target mode provides for
`
`the configuration of a server using SCSI-2 to communicate
`
`with Fibre Channel targets. This mode requires that a
`
`host system has a SCSI-2 interface and driver software to
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`15
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`control SCSI-2 target devices. The storage router will
`
`connect to the SCSI-2 bus and respond as a target to
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`multiple target IDs . Configuration information is
`
`required to identify the target IDs to which the bridge
`
`will respond on the SCSI-2 bus. The storage router then
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`translates the SCSI-2 requests to SCSI-3 FCP requests,
`
`allowing the use of FC devices with a SCSI host system.
`
`This will also allow features such as a tape device
`
`acting as an initiator on the SCSI bus to provide full
`
`support for this type of SCSI device.
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`25
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`In general, user configuration of the storage router
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`will be needed to support various functional modes of
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`operation. Configuration can be modified, for example,
`
`through a serial port or through an Ethernet port via
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`SNMP (simple network management protocol) or a Telnet
`
`session. Specifically, SNMP manageability can be
`
`provided via an 802.3 Ethernet interface. This can
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`provide for configuration changes as well as providing
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`5
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`statistics and error information. Configuration can also
`
`be performed via TELNET or RS-232 interfaces with menu
`
`driven command interfaces. Configuration information can
`
`be stored in a segment of flash memory and can be
`
`retained across resets and power off cycles. Password
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`:: ·
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`protection can also be provided.
`
`In the first two modes of operation, addressing
`
`information is needed to map from FC addressing to SCSI
`
`addressing and vice versa. This can be 'hard'
`
`configuration data, due to the need for address
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`information to be maintained across initialization and
`
`partial reconfigurations of the Fibre Channel address
`
`space.
`
`In an arbitrated loop configuration, user
`
`configured addresses will be needed for AL PAs in order
`
`to insure that known addresses are provided between loop
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`20
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`reconfigurations.
`
`With respect to addressing, FCP and SCSI 2 systems
`
`employ different methods of addressing target devices.
`
`Additionally, the inclusion of a storage router means
`
`that a method of translating device IDs needs to be
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`25
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`implemented.
`
`In addition, the storage router can respond
`
`to commands without passing the commands through to the
`
`opposite interface. This can be implemented to allow all
`
`generic FCP and SCSI commands to pass through the storage
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`router to address attached devices, but allow for
`
`configuration and diagnostics to be performed directly on
`
`the storage router through the FC and SCSI interfaces.
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`Management commands are those intended to be
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`5
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`processed by the storage router controller directly.
`
`This may include diagnostic, mode, and log commands as
`
`well as other vendor-specific commands. These commands
`
`can be received and processed by both the FCP and SCSI
`
`interfaces, but are not typically bridged to the opposite
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`interface. These commands may also have side effects on
`
`the operation of the storage router, and cause other
`
`storage router operations to change or terminate.
`
`A primary method of addressing management commands
`
`though the FCP and SCSI interfaces can be through
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`15
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`peripheral device type addressing. For example, the
`
`storage router can respond to all operations addressed to
`
`logical unit {LUN) zero as a controller device. Commands
`
`that ~he storage router will support can include INQUIRY
`
`as well as vendor-specific management commands. These
`are to be generally consistent with sec standard
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`commands.
`
`The SCSI bus is capable of establishing bus
`
`connections between targets. These targets may
`
`internally address logical units. Thus, the prioritized
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`25
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`addressing scheme used by SCSI subsystems can be
`
`represented as follows: BUS:TARGET:LOGICAL UNIT. The BUS
`
`identification is intrinsic in the configuration, as a
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`SCSI initiator is attached to only one bus. Target
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`addressing is handled by bus arbitration from information
`
`provided to the arbitrating device. Target addresses are
`
`assigned to SCSI devices directly, though some means of
`
`configuration, such as a hardware jumper, switch setting,
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`5
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`or device specific software configuration. As such, the
`
`SCSI protocol provides only logical unit addressing
`
`within the Identify message. Bus and target information
`
`is implied by the established connection.
`
`Fibre Channel devices within a fabric are addressed
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`10
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`by a unique port identifier. This identifier is assigned
`
`to a port during certain well-defined states of the FC
`
`protocol.
`
`Individual ports are allowed to arbitrate for
`
`a known, user defined address.
`
`If such an address ~s not
`
`provided, or if arbitration for a particular user address
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`15
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`fails, the port is assigned a unique address by the FC
`
`protocol. This address is generally not guaranteed to be
`
`unique between instances. Various scenarios exist where
`
`the AL-PA of a device will change, either after power
`
`cycle or loop reconfiguration.
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`20
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`The FC protocol also provides a logical unit address
`
`field within command structures to provide addressing to
`
`devices internal to a port. The FCP_CMD payload
`
`specifies an eight byte LUN field. Subsequent
`
`identification of the exchange between devices is
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`25
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`provided by the FQXID (Fully Qualified Exchange ID) .
`
`FC ports can be required to have specific addresses
`
`assigned. Although basic functionality is not dependent
`
`on this, changes in the loop configuration could result
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`PATENT APPLICATION
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`in disk targets changing identifiers with the potential
`
`risk of data corruption or loss. This configuration can
`
`be straightforward, and can consist of providing the
`
`device a loop-unique ID (AL_PA) in the range of "Olh" to
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`5
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`"EFh." Storage routers could be shipped with a default
`
`value with the assumption that most configurations will
`
`be using single storage routers and no other devices
`
`requesting the present ID. This would provide a minimum
`
`amount of initial configuration to the system
`
`,.
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`10
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`administrator. Alternately, storage routers could be
`
`defaulted to assume any address so that configurations
`
`requiring multiple storage routers on a loop would not
`
`require that the administrator assign a unique ID to the
`
`additional storage routers.
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`15
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`Address translation is needed where commands are
`
`issued in the cases FC Initiator to SCSI Target and SCSI
`
`Initiator to FC Target. Target responses are qualified
`
`by the FQXID and will retain the translation acquired at
`
`the beginning of the exchange. This prevents
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`20
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`configuration changes occurring during the course of
`
`execution of a command from causing data or state
`
`information to be inadvertently misdirected ..
`
`Configuration can be required in cases of SCSI Initiator
`
`to FC Target, as discovery may not effectively allow for
`
`25
`
`FCP targets to consistently be found. This is due to an
`
`FC arbitrated loop supporting addressing of a larger
`
`number of devices than a SCSI bus and the possibility of
`
`FC devices changing their AL-PA due to device insertion
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`ATTORNEYS DOCKET
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`PATENT APPLICATION
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`or ot