Patent Publication Number: US-2006015696-A1

Title: Integrated storage device

Description:
BACKGROUND  
      1. Field  
      Implementations of the invention relate to an integrated storage device.  
      2. Description of the Related Art  
      Computing systems often include one or more host computers (“hosts”) for processing data and running application programs, direct access storage devices (DASDs) for storing data, and a storage controller for controlling the transfer of data between the hosts and the DASD. Storage controllers, also referred to as control units or storage directors, manage access to a storage space comprised of numerous hard disk drives, otherwise referred to as a Direct Access Storage Device (DASD). Hosts may communicate Input/Output (I/O) requests to the storage space through the storage controller.  
      In many systems, data on one storage device, such as a DASD, may be copied to the same or another storage device so that access to data volumes can be provided from two different devices. A point-in-time copy involves physically copying all the data from source volumes to target volumes so that the target volume has a copy of the data as of a point-in-time. A point-in-time copy can also be made by logically making a copy of the data and then only copying data over when necessary, in effect deferring the physical copying. This logical copy operation is performed to minimize the time during which the target and source volumes are inaccessible.  
      A number of direct access storage device (DASD) subsystems are capable of performing logical copies, which may be referred to as “instant virtual copy” operations or “copy-on-write” operations. Instant virtual copy operations work by modifying metadata such as relationship tables or pointers to treat a source data object as both the original and copy. In response to a host&#39;s copy request, the storage subsystem immediately reports creation of the copy without having made any physical copy of the data. Only a “virtual” copy has been created, and the absence of an additional physical copy is completely unknown to the host.  
      Later, when the storage system receives updates to the original or copy, the updates are stored separately and cross-referenced to the updated data object only. At this point, the original and copy data objects begin to diverge. The initial benefit is that the instant virtual copy occurs almost instantaneously, completing much faster than a normal physical copy operation. This frees the host and storage subsystem to perform other tasks. The host or storage subsystem may even proceed to create an actual, physical copy of the original data object during background processing, or at another time.  
      One such instant virtual copy operation is known as a FlashCopy® operation. A FlashCopy® operation involves establishing a logical point-in-time relationship between source and target volumes on the same or different devices. The FlashCopy® operation guarantees that until a track in a FlashCopy® relationship has been hardened to its location on the target disk, the track resides on the source disk. A relationship table is used to maintain information on all existing FlashCopy® relationships in the subsystem. During the establish phase of a FlashCopy® relationship, one entry is recorded in the source and target relationship tables for the source and target that participate in the FlashCopy® relationship being established. Each added entry maintains all the required information concerning the FlashCopy® relationship. Both entries for the relationship are removed from the relationship tables when all FlashCopy® tracks from the source volumes have been physically copied to the target volumes or when a withdraw command is received. In certain cases, even though all tracks have been copied from the source volumes to the target volumes, the relationship persists.  
      The target relationship table further includes a bitmap that identifies which tracks involved in the FlashCopy® relationship have not yet been copied over and are thus protected tracks. Each track in the target device is represented by one bit in the bitmap. The target bit is set when the corresponding track is established as a target track of a FlashCopy® relationship. The target bit is reset when the corresponding track has been copied from the source and destaged to the target due to writes on the source or the target, or a background copy task.  
      Further details of the FlashCopy® operations are described in the copending and commonly assigned U.S. Pat. No. 6,661,901, issued on Aug. 26, 2003, entitled “Method, System, and Program for Maintaining Electronic Data as of a Point-in-Time”, which patent application is incorporated herein by reference in its entirety.  
      Once the logical relationship is established, hosts may then have immediate access to data on the source and target volumes, and the data may be copied as part of a background operation. A read to a track that is a target in a FlashCopy® relationship and not in cache triggers a stage intercept, which causes the source track corresponding to the requested target track to be staged to the target cache when the source track has not yet been copied over and before access is provided to the track from the target cache. This ensures that the target has the copy from the source that existed at the point-in-time of the FlashCopy® operation. Further, any destages to tracks on the source device that have not been copied over triggers a destage intercept, which causes the tracks on the source device to be copied to the target device.  
      Currently, system administrators spend a great deal of time creating backup copies of data. The current process for creating a backup copy of a database has multiple tasks. Initially, the database is mapped to source volumes (i.e., the source volumes on which the database resides are identified). For each source volume, an appropriate target volume is selected based on factors, such as the size and type of the source volume. An instant virtual copy operation is performed between the source volumes and the target volumes, which consumes an equal amount of storage space (e.g., to create a point-in-time copy of one terabyte of data requires an extra terabyte of storage space). The target volumes are assigned to the first host that requested the instant virtual copy operation (which may affect the performance of the host) or to a second host of the same type as the first host. The selected host to which the target volumes are assigned is notified about the target volumes. Optionally, the database may be made available on another host. Then, a backup/archive process at the selected host is used to read the data from the target volumes and copy the data to a third computer system, such as a backup server. If tapes are not already mounted to tape drives attached to the backup server, these are mounted. The backup server writes the data to the tapes. Then, the tapes contain a backup copy of the database. This process of creating a backup copy of the database uses up to two times the storage space of the database, up to three computer systems, and backup software. Furthermore, because of the complexity of the process, system administrators may spend a great deal of time (e.g., more than half of their time) creating backup copies. For large amounts of data, the process may also strain fibre channel and Ethernet networks because of the data movement between the three computing systems. Backup servers may also be strained by having to write large amounts of data to tape.  
      In U.S. Pat. No. 6,625,704 B2, issued on Sep. 23, 2003, to Alexander Winokur, and entitled “Data Backup Method and System Using Snapshot and Virtual Tape,” information identifying a set of data that is to be copied from a first DASD is received and destination locations are mapped in a second DASD for each element of the set. The destination locations are in a sequence emulating a tape copy.  
      Notwithstanding the usefulness of conventional systems, there is a need in the art for an integrated storage device that allows simpler creation of backup copies.  
     SUMMARY OF THE INVENTION  
      Provided are an article of manufacture, system, and method for creating a backup copy. An instant virtual copy operation is received for copying one or more blocks of data from a source storage to a target storage. For each block of data to be copied from the source storage, a location identifier for the block of data is obtained. The block of data is copied from the source storage to the target storage along with the location identifier.  
      Also, provided is a system including an integrated storage device controller. Disk storage is attached to the integrated storage device controller. One or more tape drives are attached to the integrated storage device controller. A user interface is provided by the integrated storage device controller to enable receipt of commands for direct copying of data between the disk storage and the one or more tape drives. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Referring now to the drawings in which like reference numbers represent corresponding parts throughout:  
       FIG. 1  illustrates a computing environment in which certain implementations of the invention are implemented.  
       FIG. 2  illustrates blocks of storage in accordance with certain implementations of the invention.  
       FIG. 3  illustrates various structures in accordance with certain implementations of the invention.  
       FIGS. 4A and 4B  illustrate logic for creating a backup copy of data in accordance with certain implementations of the invention.  
       FIG. 5  illustrates logic for restoring data from target storage to source storage in accordance with certain implementations of the invention.  
       FIG. 6  illustrates an architecture of a computer system that may be used in accordance with certain implementations of the invention. 
    
    
     DETAILED DESCRIPTION OF THE IMPLEMENTATIONS  
      In the following description, reference is made to the accompanying drawings which form a part hereof and which illustrate several implementations of the invention. It is understood that other implementations may be utilized and structural and operational changes may be made without departing from the scope of implementations of the invention.  
       FIG. 1  illustrates, in a block diagram, a computing environment in accordance with certain implementations of the invention. An integrated storage device  90  includes one or more integrated storage device controllers  100 , source storage  120 , and target storage  130 .  
      An integrated storage device controller  100  receives Input/Output (I/O) requests from hosts  140   a, b, . . . l  (wherein a, b, and l may be any integer value) over a communication path  190  directed toward storage devices  120 ,  130  configured to have portions of data (e.g., Logical Unit Numbers, Logical Devices, portions of tapes mounted in tape drives, etc.)  122   a, b , . . . n and  132   a, b, . . . m , respectively, where m and n may be different integer values or the same integer value. The communication path may comprise, for example, a bus or a storage area network. Thus, the hosts  140   a, b, . . . l  may be directly attached to the integrated storage device  90  or may be connected via a storage area network to the integrated storage device  90 .  
       FIG. 2  illustrates a block of storage in accordance with certain implementations of the invention. A block of storage  250  may be divided into sub-blocks of storage  250   a ,  250   b  . . .  250   p , where a, b, and p represent that there may be any number of sub-blocks of storage.  
      The source storage  120  includes one or more portions of data  122   a, b , . . . n, which may be divided into blocks of storage  250  containing blocks of data, and the blocks of storage  250  are further divided into sub-blocks of storage ( 250   a ,  250   b  . . .  250   p ) that contain sub-blocks of data. A portion of data may be any logical or physical element of storage. In certain implementations, the blocks of data are contents of tracks, while the sub-blocks of data are contents of sectors of tracks.  
      In certain implementations, target storage  130  may comprise any form of removable storage that stores data sequentially (e.g., tapes mounted on tape drives). Storage that stores data sequentially stores data in a next available consecutive portion of storage, rather than storing data randomly in the storage. That is, target storage  130  may comprise one or more sequential access storage devices. Sequential access storage devices read or write data in consecutive portions of storage or may incur a performance penalty (e.g., to rewind or forward a tape to a particular portion of storage) to read or write at non-consecutive portions of storage, whereas random access storage devices read and write from any portion of storage.  
      Target storage  130  maintains copies of all or a subset of the portions of data  122   a, b, . . . n  of the source storage  120 . Additionally, target storage  130  may be modified by, for example, host  140   a . Target storage  130  includes one or more portions of data  132   a, b . . . m , which may be divided into blocks of storage  250  containing blocks of data, and the blocks of storage  250  are further divided into sub-blocks of storage ( 250   a ,  250   b  . . .  250   p ) that contain sub-blocks of data. A portion of data may be any logical or physical element of storage. In certain implementations, the blocks of data are tracks, while the sub-blocks of data are sectors of tracks.  
      For ease of reference, the terms tracks and sectors will be used herein as examples of blocks of data and sub-blocks of data, but use of these terms is not meant to limit implementations of the invention to tracks and sectors. The implementations of the invention are applicable to any type of storage, block of storage or block of data divided in any manner. Moreover, although implementations of the invention refer to blocks of data, alternate implementations of the invention are applicable to sub-blocks of data.  
      In certain implementations, the source storage  120  is a disk device, and the target storage  130  is a tape device. Thus, certain implementations of the invention provide an integrated disk and tape device. In certain implementations, the source storage  120  may comprise an array of storage devices, such as Just a Bunch of Disks (JBOD), Redundant Array of Independent Disks (RAID), a virtualization device, etc. In certain implementations, the tape device is an automated tape library, containing one or more tape drives, storage for a large number of tapes, and a robotic arm to automatically mount and unmount tapes into the tape drives from the tape library. In certain implementations, the integrated storage device  90  comprises one or more storage controllers, attached via high speed links (e.g., Fibre Channel links) to the disk device and tape device.  
      The integrated storage device controller  100  includes a source cache  124  in which updates to tracks in the source storage  120  are maintained until written to source storage  120  (i.e., the tracks are destaged to physical storage). The integrated storage device controller  100  includes a target cache  134  in which updates to tracks in the target storage  130  are maintained until written to target storage  130  (i.e., the tracks are destaged to physical storage). The source cache  124  and target cache  134  may comprise separate memory devices or different sections of a same memory device. The source cache  124  and target cache  134  are used to buffer read and write data being transmitted between the hosts  140   a, b, . . . l , source storage  120 , and target storage  130 . Further, although caches  124  and  134  are referred to as source and target caches, respectively, for holding source or target blocks of data in a point-in-time copy relationship, the caches  124  and  134  may store at the same time source and target blocks of data in different point-in-time relationships.  
      Additionally, the integrated storage device controller  100  includes a nonvolatile cache  118 . The non-volatile cache  118  may be, for example, a battery-backed up volatile memory, to maintain a non-volatile copy of data updates.  
      The integrated storage device controller  100  further includes system memory  110 , which may be implemented in volatile and/or non-volatile devices. The system memory  110  includes a read process  112  for reading data, a write process  114  for writing data, and a direct backup process  116 . The read process  112  executes in system memory  110  to read data from storages  120  and  130  to caches  124  and  134 , respectively. The write process  114  executes in system memory  110  to write data from caches  124  and  134  to storages  120  and  130 , respectively. The direct backup process  116  executes in system memory  110  to create a backup copy of data from all or a portion of source storage  120  to target storage  130 .  
      In certain implementations, the integrated storage device  90  contains two or more storage controllers, a disk device, and a tape device. The direct backup process  116  may span the storage controllers, may execute on each storage controller or may execute within the single integrated storage device  90 .  
      Also, the system memory  110  may be in a separate memory device from caches  124  and  134  or may share a memory device with one or both caches  124  and  134 .  
      Implementations of the invention are applicable to the transfer of data between any two storage mediums, which for ease of reference will be referred to herein as source storage and target storage or as first storage and second storage. For example, certain implementations of the invention may be used with two storage mediums located at a single storage controller. Moreover, certain alternative implementations of the invention may be used with two storage mediums connected to different storage controllers. Also, for ease of reference, a block of data in source storage will be referred to as a “source block of data,” and a block of data in target storage will be referred to as a “target block of data.” 
      In certain implementations, the integrated storage device controller  100  comprises a storage controller, which may further include a processor complex (not shown) and may comprise any storage controller or server known in the art, such as an Enterprise Storage Server® (ESS), 3990®Storage Controller, etc. The hosts  140   a, b, . . . l  may comprise any computing device known in the art, such as a server, mainframe, workstatation, personal computer, hand held computer, laptop telephony device, network appliance, etc.  
      The integrated storage device controller  100  and host system(s)  140   a, b, . . . l  communicate via a communication path  190 , which may comprise a network (e.g., a Storage Area Network (SAN), a Local Area Network (LAN), Wide Area Network (WAN), the Internet, an Intranet, etc.) or a direct attachment technology (e.g., Small Computer System Interface (SCSI) or Serial ATA).  
      Additionally, although  FIG. 1  illustrates a single integrated storage device  90 , one skilled in the art would know that multiple integrated storage devices may be connected via a network (e.g., a Local Area Network (LAN), Wide Area Network (WAN), the Internet, etc.), and one or more of the multiple integrated storage devices may implement the invention.  
      Hosts  140   a, b, . . . l  attach to the integrated storage device controller  100  and use the integrated storage device controller  100  like a storage controller. The integrated storage device controller  100 , however, is capable of creating a backup copy from source storage  120  directly to target storage  130  that comprises removable storage that stores data sequentially.  
       FIG. 3  illustrates a copy structure  310  in accordance with certain implementations of the invention. Copy structure  310  may be stored in nonvolatile cache  118  or in system memory  110  of the integrated storage device controller  100 . A copy structure  310  is used to monitor which blocks of data within portions of data in the source storage  120  have been copied to target storage  130 . The copy structure  310  includes an indicator (e.g., a bit) for each block of data in the source storage  120  that is part of the incremental virtual copy relationship. When an indicator is set to a first value (e.g., one), the setting indicates that the block of data has been copied to target storage  130 . When an indicator is set to a second value (e.g., zero), the setting indicates that the block of data has not been copied to target storage  130 . For example, in copy structure  310 , the indicators of “X” indicate that blocks of data associated with the X indicators have been copied to storage, while indicators of “Y” indicate that blocks of data associated with the Y indicators have not been copied to storage.  
      In certain implementations of the invention, copy structure  310  comprises a bitmap, and each indicator comprises a bit. In certain implementations, for copy structure  310 , the nth indicator corresponds to an nth block of data (e.g., the first indicator in structure  310  corresponds to a first block of data). In certain implementations of the invention, there is a copy structure  310  for each portion of data. In certain alternative implementations of the invention, there is a single copy structure  310  for all portions of data at source storage  120 .  
       FIGS. 4A and 4B  illustrate logic for creating a backup copy of data in accordance with certain implementations of the invention. Control begins at block  400  with the direct backup process  116  receiving an instant virtual copy operation for creating a backup copy of data at source storage  120  to target storage  130 . In certain implementations, users and/or application programs may invoke the instant virtual copy operation. In certain implementations, a user interface (e.g., a graphical user interface) is provided by implementations of the invention to enable scheduling of backup copies. For example, periodically (e.g., every night), the integrated storage device controller  100  halts certain Input/Output (I/O) operations to the source storage  120  and performs the instant virtual copy operation to store data from source storage  120  to target storage  130 , which is removable storage that stores data sequentially. In certain implementations, both read operations and write operations are halted. In certain other implementations, write operations are suspended and read operations are allowed to continue. The removable storage may then be removed and, for example, sent by a system administrator for offsite storage.  
      In block  402 , the direct backup process  116  halts certain I/O operations (e.g., read and write operations or only write operations) on the source storage  120 . In block  404 , the direct backup process  116  creates copy structure  310 . In particular, all of the indicators in the copy structure  310  are set to indicate that the blocks of data associated with the indicators are to be copied to target storage. In certain implementations, the copy structure  310  has already been created, and the processing of block  404  updates the copy structure  310 . In block  406 , the direct backup process  116  resumes I/O operations on the source storage  120 .  
      From block  406  ( FIG. 4A ), processing continues to block  408  ( FIG. 4B ). In block  408 , the direct backup process  116  starts a background copy from source storage to target storage to store blocks of data with location identifiers. The location identifiers identify the location of the block of data in source storage  120  relative to other blocks of data. In certain implementations, the location identifiers are sequence identifiers. In certain implementations, the location identifiers are offsets from a base position in source storage  120 . In certain implementations, the location identifier is generated for a block of data when that block of data is to be copied to target storage  130 . In certain implementations, the location identifiers are generated and stored with the blocks of data on source storage  120 , and when a block of data is copied to target storage  130 , the block of data is copied along with its location identifier. In certain implementations, the location identifier is 64-bits.  
      In block  410 , the direct backup process  116  determines whether the background copy is done. If so, processing continues to block  412 , otherwise, processing continues to block  414 . In block  412 , the backup copy on removable storage may be stored (e.g., offsite or in a tape library) and normal read/write operations resume. In particular, read and write operations continue to occur during the background operation, but they are not handled in a “normal” manner, instead they are handled as described with reference to blocks  414 - 424 .  
      For example, if the target storage  130  is a tape library with a set of one or more tape drives for holding tapes, a tape may be ejected from a tape drive for storage in the tape library. Alternatively, a tape may be left in a tape drive and may be ejected as needed (e.g., when a new backup copy is to be made onto another set of one or more tapes). In some cases, a system administrator may also make a copy of a tape and send the tape off site for secure storage.  
      In block  414 , the direct backup process  116  determines whether a read request for a block of data has been received. If so, processing continues to block  416 , otherwise, processing continues to block  418 . In block  416 , the read request is performed from source storage. From block  416 , processing loops back to block  410 .  
      In block  418 , the direct backup process  116  determines whether a write request for a block of data has been received. If so, processing continues to block  420 , otherwise, processing loops back to block  410 . In block  420 , the direct backup process  116  determines whether an indicator is set for the block of data to indicate that the block of data still needs to be copied from source storage  120  to target storage  130 . If so, processing continues to block  422 , otherwise, processing continues to block  424 . In block  422 , the direct backup process  116  copies the block of data to target storage  130  with a location identifier and processing continues to block  424 . In block  424 , the write request is performed at source storage  120 .  
      It is possible that when a write request for a block of data is received, the background copy has not copied one or more blocks of data sequentially prior to the block of data to be written. For example, for blocks of data with sequence numbers  100 ,  101 ,  102 ,  103 , and  104 , it is possible that blocks of data with sequence numbers  100  and  101  have been copied from source storage  120  to target storage  130 , a write request is received for block of data with sequence number  104 , and blocks of data with sequence numbers  102  and  103  have not been copied from source storage  120  to target storage  130 . In this case, to avoid holding up the write request, the direct backup process  116  copies the data block with sequence number  104  from source storage  120  to target storage  130 , along with a location identifier that indicates the location of the block of data with sequence number  104  with respect to other blocks of data at source storage  120  that are part of the instant virtual copy relationship. Then, the backup copy continues and, in this example, blocks of data with sequence numbers  102  and  103  are copied to target storage  130 . Note that each block of data copied to target storage  130  is stored with a location identifier. The location identifiers are used because the target storage  130  stores data in sequential positions in storage (rather than in random positions, which would allow for allocating space for blocks of data with sequence numbers  102  and  103  when writing block of data with sequence number  104  from the above example).  
      When data is to be restored from target storage  130  to source storage  120 , the location identifiers are used to order the blocks of data.  FIG. 5  illustrates logic for restoring data from target storage to source storage in accordance with certain implementations of the invention. Control begins at block  500  with receipt of a request to restore a backup copy that identifies the backup copy to be restored. Each backup copy may be stored at target storage  130  with an identifier, such as a timestamp, a user or system administrator provided name, etc. Additionally, each backup copy identifies the portions of data (e.g., volumes) of source storage  120  that were copied to target storage  130 . Then, a user or system administrator may specify which backup copy to restore using, for example, a user interface provided by implementations of the invention.  
      In block  502 , one or more removable storages are loaded at the integrated storage device controller  100 . For example, the removable storages may be one or more tapes that are mounted on tape drives of a tape library attached to the integrated storage device controller  100 .  
      In certain implementations, when target storage  130  is a tape library, a system administrator may issue the command to restore a certain backup copy. In response to that command, the integrated storage device controller  100  automatically selects the correct tape from the tape library that stores the certain backup copy and mounts the tape into a tape drive.  
      In block  504 , the direct backup process  116  takes selected portions of data (e.g., volumes) of source storage  120  offline. The selected portions of data correspond to portions of data to be restored with the backup copy on target storage  130 .  
      In block  506 , the direct backup process  116  performs the restore from the target storage  130  to source storage  120  using the location identifiers of blocks of data to determine the ordering of the blocks of data on source storage  120 . Performing the restore comprises copying blocks of data from target storage  130  to source storage  120 . In certain implementations in which the target storage  130  is a tape library and source storage  120  is a disk device, the restore is performed by reading a block of data sequentially from a tape and writing the data to the disk device in its correct location using the location identifier. In some implementations, the direct backup process  116  may read several blocks of data from tape and sort them before writing the blocks of data to the disk device.  
      In certain implementations, target storage  130  is a first target storage  130  and there is a second target storage (not shown in  FIG. 1 ), which resides on random access storage. The processing of block  506  is performed to restore blocks of data from the first target storage  130  to the second target storage. Then, certain I/O operations (e.g., read and write operations or only write operations) are halted on source storage  120 , and an instant virtual copy (e.g., FlashCopy® operation) is performed from the second target storage to the source storage  120 . In block  508 , after the copy is logically complete, the direct backup process  116  brings the selected portions of data of source storage  120  online. In block  510 , I/Os are resumed to source storage  120 .  
      In certain alternative implementations, a process other than the direct backup process  116  (e.g., a direct restore process that resides in system memory  110  (not shown)) may perform the processing of blocks  504 ,  506 , and  508 .  
      Example scenarios will be provided merely to enhance understanding of the invention. In one example scenario, the source storage  120  is a disk device and the target storage  130  is a tape library. To create a backup copy, blocks of data are copied directly from the disk device to a tape via an instant virtual copy operation. Then, to restore the backup copy on tape, blocks of data are copied directly from the tape to the disk device.  
      In another example scenario, it is possible to create an instant virtual copy from Storage A to Storage B, create an instant virtual copy from Storage B to tape, and eject the tape for off-site storage once a background copy from Storage B is complete. Then, at restore time, if Storage B contains a good copy of data, an instant virtual copy from Storage B to Storage A may be performed. However, if data at Storage B is corrupt or if an older version of a backup copy is to be restored from tape, the tape may be inserted at the integrated storage device controller  100 , data may be copied from tape to Storage B, and then the data may be copied from Storage B to Storage A via an instant virtual copy operation.  
      Thus, implementations of the invention eliminate the need for multiple computing systems and complex backup software. Also, implementations of the invention eliminate the need for target disk space by copying data from source storage  120  to tape in random order, along with a location identifier that allows data to be restored to its proper location on source storage  120 .  
      For example, assuming 512-byte blocks and an 8-byte location identifier, it is expected that there would be a 1.5% overhead for creating backup copies, whereas conventional solutions have as much as a 100% overhead. Additionally, in certain implementations, four or more tape drives are used to stripe data for better performance. Assuming that IBM® 3592 Enterprise tape drives are used with 2:1 compaction, four tape drives provide 320 megabytes/second of throughput, which is faster than most disk to disk instant virtual copies.  
      IBM is a registered trademark or common law mark of International Business Machines Corporation in the United States and/or foreign countries.  
     Additional Implementation Details  
      The described implementations may be implemented as a method, apparatus or article of manufacture using programming and/or engineering techniques to produce software, firmware, hardware, or any combination thereof. The terms “article of manufacture” and “circuitry” as used herein refer to a state machine, code or logic implemented in hardware logic (e.g., an integrated circuit chip, Programmable Gate Array (PGA), Application Specific Integrated Circuit (ASIC), etc.) or a computer readable medium, such as magnetic storage medium (e.g., hard disk drives, floppy disks, tape, etc.), optical storage (CD-ROMs, optical disks, etc.), volatile and non-volatile memory devices (e.g., EEPROMs, ROMs, PROMs, RAMs, DRAMs, SRAMs, firmware, programmable logic, etc.). Code in the computer readable medium is accessed and executed by a processor. When the code or logic is executed by a processor, the circuitry may include the medium including the code or logic as well as the processor that executes the code loaded from the medium. The code in which embodiments are implemented may further be accessible through a transmission media or from a server over a network. In such cases, the article of manufacture in which the code is implemented may comprise a transmission media, such as a network transmission line, wireless transmission media, signals propagating through space, radio waves, infrared signals, etc. Thus, the “article of manufacture” may comprise the medium in which the code is embodied. Additionally, the “article of manufacture” may comprise a combination of hardware and software components in which the code is embodied, processed, and executed. Of course, those skilled in the art will recognize that many modifications may be made to this configuration, and that the article of manufacture may comprise any information bearing medium known in the art.  
      The logic of  FIGS. 4A, 4B , and  5  describes specific operations occurring in a particular order. In alternative implementations, certain of the logic operations may be performed in a different order, modified or removed. Moreover, operations may be added to the above described logic and still conform to the described implementations. Further, operations described herein may occur sequentially or certain operations may be processed in parallel, or operations described as performed by a single process may be performed by distributed processes.  
      The illustrated logic of  FIGS. 4A, 4B , and  5  may be implemented in software, hardware, programmable and non-programmable gate array logic or in some combination of hardware, software, or gate array logic.  
       FIG. 6  illustrates an architecture  600  of a computer system that may be used in accordance with certain implementations of the invention. Integrated storage device controller  100  and/or hosts  140   a, b, . . . l  may implement computer architecture  600 . The computer architecture  600  may implement a processor  602  (e.g., a microprocessor), a memory  604  (e.g., a volatile memory device), and storage  610  (e.g., a non-volatile storage area, such as magnetic disk drives, optical disk drives, a tape drive, etc.). An operating system  605  may execute in memory  604 . The storage  610  may comprise an internal storage device or an attached or network accessible storage. Computer programs  606  in storage  610  may be loaded into the memory  604  and executed by the processor  602  in a manner known in the art. The architecture further includes a network card  608  to enable communication with a network. An input device  612  is used to provide user input to the processor  602 , and may include a keyboard, mouse, pen-stylus, microphone, touch sensitive display screen, or any other activation or input mechanism known in the art. An output device  614  is capable of rendering information from the processor  602 , or other component, such as a display monitor, printer, storage, etc. The computer architecture  600  of the computer systems may include fewer components than illustrated, additional components not illustrated herein, or some combination of the components illustrated and additional components.  
      The computer architecture  600  may comprise any computing device known in the art, such as a mainframe, server, personal computer, workstation, laptop, handheld computer, telephony device, network appliance, virtualization device, storage controller, etc. Any processor  602  and operating system  605  known in the art may be used.  
      The foregoing description of implementations of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the implementations of the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of the implementations of the invention be limited not by this detailed description, but rather by the claims appended hereto. The above specification, examples and data provide a complete description of the manufacture and use of the composition of the implementations of the invention. Since many implementations of the invention can be made without departing from the spirit and scope of the implementations of the invention, the implementations of the invention reside in the claims hereinafter appended or any subsequently-filed claims, and their equivalents.