Abstract:
A system comprising an interface, a plurality of storage arrays, a data processing module, and a switch module. The interface receives data blocks from a host via a network. The data processing module connected between the interface and the plurality of storage arrays, wherein the data processing module is configured to (i) determine which ones of the data blocks each of a plurality of target processing modules of the storage arrays is to perform error checking and correcting processing, and (ii) transfer each of the data blocks from the interface to a respectively assigned one of the plurality of target processing modules. The switch module provides communication paths between the data processing module and the plurality of storage arrays.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This present disclosure is a continuation of U.S. application Ser. No. 11/724,549, filed on Mar. 15, 2007, which is a continuation of U.S. application Ser. No. 11/591,325 (now U.S. Pat. No. 7,634,686), filed on Nov. 1, 2006, which claims priority under 35 U.S.C. §119(e) to U.S. Provisional Application No. 60/820,180, filed on Jul. 24, 2006. 
     
    
     FIELD 
       [0002]    The present disclosure relates to redundant arrays of independent disks (RAID) systems. 
       BACKGROUND 
       [0003]    The Background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the tithe of filing, are neither expressly or impliedly admitted as prior art against the present disclosure. 
         [0004]    A redundant array of independent disks (RAID) system redundantly stores data on multiple hard disks. In some RAID levels, data blocks are split and stored on different disks, which reduces data storage and retrieval latency. Multiple disks also tend to increase mean time between failures (MTBF) and increases fault tolerance. 
         [0005]    The RAID system appears to an accessing or host device as a single logical hard disk drive. The RAID system may employ disk striping, which involves partitioning the storage space of each drive into units. The size of the units will vary depending upon the application from a sector (512 bytes) up to several megabytes. The stripes of all the disks are typically interleaved and addressed in order. 
         [0006]    There are many types of RAID systems in addition to a non-redundant array (RAID-0). In RAID-0, striping is employed without redundancy of data. It offers the best performance but no fault-tolerance. In RAID-1, disk mirroring is used without striping and at least two drives are required to allow duplication during storage of data. Read performance is improved since either disk can be read at the same time. Write performance is the same as single disk storage. RAID-1 provides the best performance and the best fault-tolerance in a multi-user system. 
         [0007]    In RAID-2, striping across disks is used. Some disks store error checking and correcting (ECC) information. In RAID-3, striping is used and one drive is dedicated to storing parity information. The embedded error checking (ECC) information is used to detect errors. Data recovery is accomplished by calculating the exclusive OR (XOR) of the information recorded on the other drives. Since an I/O operation addresses all drives at the same time, RA/D-3 cannot overlap I/O. As a result, RAID-3 is best for single-user systems with long record applications. 
         [0008]    In RAID-4, large stripes are used. Records can be read from any single drive. This allows overlapped I/O for read operations. Since write operations update the parity drive, no I/O overlapping is possible. In RAID-5, a rotating parity array is used, which addresses write limitations of RAID-4. Thus, read and write operations can be overlapped. RAID-5 stores parity information but does not use redundant data. However, the parity information can be used to reconstruct data. RAID-5 requires at least three and usually five disks for the array. RAID-5 is best for multi-user systems in which performance is not critical or which do few write operations. 
         [0009]    RAID-6 is similar to RAID-5 except that a second parity scheme that is distributed across different drives is used. RAID-6 offers high fault- and drive-failure tolerance. In RAID-7, a real-time embedded operating system and controller are used. RAID-7 uses caching via a high-speed bus and other characteristics of a stand-alone computer. 
         [0010]    RAID-10 combines RAID-0 and RAID-1. There are two subtypes: In RAID-0+1, data is organized as stripes across multiple disks, and then the striped disk sets are mirrored; and in RAID-1+0, the data is mirrored and the mirrors are striped. 
         [0011]    In RAID-50 (or RAID-5+0), a series of RAID-5 groups are used. The groups are striped in RAID-0 fashion to improve RAID-5 performance without reducing data protection. In RAID-53 (or RAID-5+3), striping (in RAID-0 style) is used for RAID-3&#39;s virtual disk blocks. This offers higher performance than RAID-3 but at much higher cost. 
         [0012]    When the host device sends a data block for storage, RAID processing is performed for the selected RAID approach. The RAID processing may include redundancy and recovery processing (such as error checking and correcting (ECC)) for the selected RAID level and/or other processing. 
         [0013]    In one approach, a single central processing unit (CPU) receives data blocks from another device. The CPU handles all of the RAID processing including ECC. With this approach, the CPU can often rate-limit data storage since processing relating to ECC can be variable and time consuming. In other words, processing in the CPU may cause a bottleneck and increase latency. With a single CPU, the RAID construction for one data block needs to be completed before a subsequent data block can be processed. 
       SUMMARY 
       [0014]    A redundant array of independent disks (RAID) system comprises N storage arrays, wherein each of the N storage arrays comprise a target processing module and 1 to M hard disk drives, where M and N are integers greater than 1. A data processing module assigns a first data storage request for a first data block to one of the target processing modules for processing of error checking and correcting (ECC) data for the first data block. The one of the target processing modules sends a first portion of the first data block and ECC data associated with the first data block to another of the target processing modules. 
         [0015]    In other features, the ECC data received by the another of the target processing modules corresponds to the first portion. An interface that receives the first data block and that forwards the first data block to the data processing module. The interface comprises at least one of a network interface, a Gigabit Ethernet network interface and a data bus. A switch module switches data between the data processing module and the N storage arrays and between the N storage arrays. The switch module comprises a multi-port high speed switch. The data processing module assigns a second data storage request for a second data block to a second target processing module for processing of ECC data for the second data block, wherein the second target processing module sends a first portion of the second data block and ECC data associated with the second data block to a third one of the target processing modules. The first and second data blocks are processed in an overlapping manner in the one of the target processing modules and the second target processing modules, respectively. 
         [0016]    In other features, the data processing module comprises an interface, memory, and at least one processor. The data processing module performs file system (FS) protocol functions on the first data block. The FS protocol comprises at least one of Network File Server (NFS) and Common Internet File Server (CIFS). The data processing module determines a level of RAID storage to be applied to the first data block. The data processing module maps the first data block to selected ones of the N storage arrays and updates a storage map for the N storage arrays. 
         [0017]    In other features, when the data processing module receives a data retrieval request, the data processing module assigns the data retrieval request to a first one of the target processing modules. The first one of the target processing modules retrieves data corresponding to the data retrieval request from others of the target processing modules and ECC data relating to portions of the data having errors. 
         [0018]    In other features, the first one of the target processing modules performs data recovery on the portions using the ECC data. When the data processing module receives a data retrieval request, the data processing module sends data retrieval messages to the target processing modules having data corresponding to the data retrieval request. The target processing modules retrieve the data corresponding to the data retrieval request and ECC data relating to portions of the data having errors. The target processing modules send the retrieved data corresponding to the data retrieval request and the ECC data to the data processing module, and wherein the data processing module performs data recovery on the portions using the ECC data. The target processing modules perform data recovery on the portions using the ECC data. 
         [0019]    A redundant array of independent disks (RAID) system comprises N storage arrays, wherein each of the N storage arrays comprise a target processing module and 1 to M hard disk drives, where M and N are integers greater than 1. A data processing module selectively assigns error checking and correcting (ECC) processing for data blocks to selected ones of the target processing modules in a non-overlapping manner. A switch module provides communication paths between the data processing module and the N storage arrays and between each one of the N storage arrays and others of the N storage arrays. 
         [0020]    In other features, the data processing module assigns a data storage request for a first data block to one of the target processing modules for processing of ECC data for the first data block, and wherein the one of the target processing modules sends a first portion of the first data block and ECC data associated with the first data block to another of the target processing modules. The ECC data received by the another of the target processing modules corresponds to the first portion. An interface receives the data blocks and forwards the data blocks to the data processing module. The interface comprises at least one of a network interface, a Gigabit Ethernet network interface and a data bus. 
         [0021]    In other features, the switch module comprises a multi-port high speed switch. The switch module includes a multi-port switch that operates at speeds greater than or equal to 1 Gigabit per second. The switch module includes a multi-port Gigabit Ethernet switch. The data processing module assigns a second data storage request for a second data block to a second target processing modules for processing of ECC data for the second data block. The second target processing module sends a first portion of the second data block and ECC data associated with the second data block to a third one of the target processing modules. 
         [0022]    In other features, the first and second data blocks are processed in an overlapping manner in the one of the target processing modules and the second target processing modules, respectively. The data processing module comprises an interface, memory, and at least one processor, and wherein the data processing module performs file system (FS) protocol functions on the first data block. The FS protocol comprises at least one of Network File Server (NFS) and Common Internet File Server (CIFS). The data processing module determines a level of RAID storage to be applied to the data blocks. The data processing module maps the data blocks to selected ones of the N storage arrays and updates a storage map for the N storage arrays. 
         [0023]    In other features, when the data processing module receives a data retrieval request, the data processing module assigns the data retrieval request to a first one of the target processing modules. The first one of the target processing modules requests data corresponding to the data retrieval request from others of the target processing modules and ECC data relating to portions of the data having errors. The first one of the target processing modules performs data recovery on the portions using the ECC data. 
         [0024]    In other features, when the data processing module receives a data retrieval request, the data processing module sends data retrieval messages to the target processing modules having data corresponding to the data retrieval request. The target processing modules retrieve the data corresponding to the data retrieval request and ECC data relating to portions of the data having errors. The target processing modules send the retrieved data corresponding to the data retrieval request and the ECC data to the data processing module, and wherein the data processing module performs data recovery on the portions using the ECC data. The target processing modules perform data recovery on the portions using the ECC data. 
         [0025]    Further areas of applicability of the present disclosure will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the disclosure, are intended for purposes of illustration only and are not intended to limit the scope of the disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]    The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein: 
           [0027]      FIG. 1  is a functional block diagram of a RAID system according to the present disclosure; 
           [0028]      FIG. 2A  is a functional block diagram of a data processing module; 
           [0029]      FIG. 2B  is a functional block diagram of a target processing module; 
           [0030]      FIG. 2C  is a more detailed functional block diagram of an exemplary target processing module; 
           [0031]      FIG. 3  is a functional block diagram illustrating processing of data blocks; 
           [0032]      FIG. 4  is a functional block diagram illustrating processing of data blocks; 
           [0033]      FIG. 5  is a functional block diagram illustrating processing of data blocks; 
           [0034]      FIG. 6  illustrates timing of processing of data blocks; 
           [0035]      FIG. 7  is a flowchart illustrating a method for processing data blocks for storage; 
           [0036]      FIGS. 8A and 8B  are flowcharts illustrating exemplary methods for retrieving data blocks with ECC processing performed by the data processing module; 
           [0037]      FIGS. 9A and 9B  are flowcharts illustrating exemplary methods for retrieving data blocks with ECC processing performed by a respective ones of the target processing modules; and 
           [0038]      FIG. 10  is a flowchart illustrating an exemplary method for retrieving data blocks with ECC processing performed by a selected one of the target processing modules. 
       
    
    
     DETAILED DESCRIPTION 
       [0039]    The following description is merely exemplary in nature and is in no way intended to limit the disclosure, its application, or uses. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements. As used herein, the term module, circuit and/or device refers to an Application Specific Integrated Circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that execute one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A or B or C), using a non-exclusive logical or. It should be understood that steps within a method may be executed in different order without altering the principles of the present disclosure. 
         [0040]    Referring now to  FIG. 1 , a redundant array of independent disks (RAID) system  100  is shown. An interface  104  receives blocks of data for storage in the RAID system  100 . For example, the interface  104  may be a high speed interface such as Gigabit Ethernet network interface, a data bus, etc., although any other type of interfaces may be used. A data processing module  108  performs part of the RAID processing. In other words, the data processing module  108  receives the data blocks from the interface  104  and performs operating system (OS) and file system (FS) protocol functions on the data. For example, the FS protocol may include Network File Server (NFS), Common Internet File Server (CIFS) and/or other suitable protocols. The data processing module  108  distributes redundancy and recovery processing (such as error checking and correcting (ECC)) to other target processing devices as will be described below. 
         [0041]    The data processing module  108  communicates with a switch module  112 . For example only, the switch module  112  may be a multi-port high speed switch such as a crossbar switch, a Gigabit switch or a Gigabit Ethernet switch. The switch module  112  may switch data organized as data packets. As can be appreciated, the switch module  112  provides scalability and flexibility as compared to hardwired connections. 
         [0042]    The switch module  112 , in turn, communicates with two or more storage arrays  120 - 1 ,  120 - 2 , . . . , and  120 -X (collectively storage arrays  120 ), where X is an integer greater than 1. Each of the storage arrays  120  includes target processing modules  122 - 1 ,  122 - 2 , . . . , and  122 -X, respectively, (collectively target processing modules  122 ) and one or more hard disk drives (HDDs)  124 - 11 ,  124 - 12 , . . . , and  124 -XY, (collectively HDDs  124 ) where Y is an integer greater than zero. As can be appreciated, the number of storage arrays  120  and HDDs  124  in each storage array  120  may be varied to allow scaling. 
         [0043]    Referring now to  FIG. 2A , an exemplary data processing module  108  is shown in further detail. The data processing module  108  receives data blocks for data storage via the interface  104 . The data processing module  108  may include an interface  150 , memory  154 , and one or more processors  156 . 
         [0044]    The data processing module  108  may determine a level of RAID storage to be applied, handle FS-related processing, may map the data blocks to the storage arrays, assign RAID redundancy and recovery processing (such as error checking and correcting (ECC)) to a selected target processing module, and may update a storage map, etc. 
         [0045]    The target processing module  122  that is assigned to perform the RAID redundancy and recovery processing receives instructions from the data processing module  108 . The selected target processing module  122  generates error checking and correcting (ECC) for the assigned data block. Upon completion, the target processing module  122  performs data spreading by selectively sending portions of the data block and/or ECC data to the other target processing modules for storage in the other arrays based on RAID instructions provided by the data processing module  108 . Some data and ECC data may also be stored locally. 
         [0046]    Concurrently, other target processing modules  122  can be assigned RAID redundancy and recovery processing for other data blocks. The other target processing modules  122  process ECC for other data blocks in an overlapping manner. Since the data processing module  108  does not handle ECC for any of the data blocks to be stored, the data processing module  108  no longer causes bottlenecks. The memory  154  associated with the data processing module  108  may store and update a global drive map  158  of data in the storage arrays  120 . 
         [0047]    Referring now to  FIG. 2B , each of the target processing modules  122  may include a RAID construction module  168  and a RAID retrieval module  170 . The RAID construction module  168  processes ECC. The RAID retrieval module  170  processes RAID retrieval requests as will be described below. 
         [0048]    The RAID construction module  170  processes ECC for portions of the data block that are to be stored on local drives  124  associated with the selected target processing module  122 . In addition, the RAID construction module  170  processes ECC for remote drives associated with remote storage arrays  120 . A RAID instruction module  172  generates RAID instructions for other target processing and may handle RAID instructions received from other target processing modules  122 . The RAID instruction module  172  may be integrated with the RAID construction module  170 . 
         [0049]    The remote storage arrays  120  associated with target processing modules other than the selected target processing module store the data and/or ECC data received from the selected target processing module. The remote storage arrays  120  may simply follow the RAID instructions sent by the selected target processing module  122 . 
         [0050]    As can be appreciated, the amount of processing performed by the remote storage arrays  120  is significantly lower than the RAID construction processing performed by the target processing module  122 . This allows the target processing modules  122  of the remote storage arrays  120  to be available to process RAID construction for other data blocks in an overlapping manner. 
         [0051]    Referring now to  FIG. 2C , an exemplary target processing module  122  is shown in further detail. The target processing module  122  receives requests to perform RAID construction from the data processing module and/or RAID instructions sent by remote target processing modules via the switch module  112 . The target processing module  122  includes an interface  178 , memory  182  and one or more processors  184 . 
         [0052]    Referring now to  FIG. 3 , in use a first data block  200 - 1  is received via the interface  104  at the data processing module  108 . The data processing module  108  performs OS and FS protocol functions on the data block. The data processing module  108  assigns the data block to a target processing module  122  associated with one of the storage arrays  120 . Additionally, the data processing module  122  may determine a level of RAID storage to be applied, may map the data blocks to the storage arrays, may update a storage map, etc. 
         [0053]    For example, the first data block  200 - 1  may be assigned to the target processing module  122 - 1  of the first storage array  120 - 1 . The selected target processing module  122 - 1  generates ECC for the data block. While storage array  120 - 1  is generating ECC for the first data block, the data processing module  108  receives a second data block  200 - 2  via the interface  104 . The data processing module  108  assigns the second data block to the target processing module  122 - 2  associated with the storage array  120 - 2  for ECC generation. 
         [0054]    Overlapping the handling of RAID construction processing for data blocks can continue for additional data blocks  200 -P until all of the target processing modules are handling data blocks. As a result, throughput may be significantly increased as compared to other approaches. 
         [0055]    Referring now to  FIGS. 4 and 5 , processing of the data block  200 - 1  is shown in further detail. After processing, the data processing module  108  sends the data block  200 - 1  to the target processing module  122 - 1  of the storage array  120 - 1 . The data processing module  108  may also update the drive map. The target processing module  122 - 1  processes ECC for the data block. The target processing module  122 - 1  may store some of the data associated with the data block  200 - 1  on the local drives  124  associated with the storage array  120 - 1 . In addition, the target processing module  122 - 1  may send RAID instructions, data and/or ECC data to target processing modules  122 - 2 , . . . , and  122 -X associated with other storage arrays. The other target processing modules  122 - 2 , . . . , and  122 -X in the remote storage arrays  120 - 2 , . . . , and  120 -X simply follow the RAID instructions and have limited processing burden, which leaves these target processing modules  122 - 2 , . . . , and  122 -X of the remote storage arrays  120 - 2 , . . . , and  120 -X free to handle ECC for other data blocks. 
         [0056]    In  FIG. 5 , the data processing module  108  receives a second data block  200 - 2  while the target processing module  122 - 1  is processing ECC for the first data block  200 - 1 . The data processing module  108  assigns the second data block  200 - 2  to the target processing module  122 - 2  associated with the storage array  120 - 2 . Additional data blocks  200 -P can be assigned to target processing modules  122  of other storage arrays  120 . 
         [0057]    Referring now to  FIG. 6 , exemplary RAID processing of data blocks is shown generally at  250 . This type of RAID processing can encounter bottlenecks, which reduces data access and retrieval times. Data processing according to some implementations of the present disclosure is shown at  252 . RAID construction for the data blocks may take a variable amount of time. The RAID system according to the present disclosure can continue to handle data blocks even when one of the storage requests is taking a significantly longer amount of time to process. 
         [0058]    Referring now to  FIG. 7 , a method for operating the RAID system during a data storage request is shown. Control begins with step  300 . In step  302 , control determines whether a data block for storage is received at the data processing module  108 . If step  302  is true, the data processing module  108  assigns the ECC processing for the data block to one of multiple target processing modules  122  in step  304 . The data processing module  108  may also update the global drive map and may perform other functions described above. In step  306 , the selected target processing module processes the ECC for the data block. The selected target processing module may send RAID instructions, data and/or ECC data to remote target processing modules associated with remote storage arrays. Control ends with step  310 . 
         [0059]    Referring now to  FIGS. 8A-10 , various exemplary methods for data retrieval are illustrated. For data retrieval, ECC processing may be performed when errors are detected upon retrieval. The errors may be detected by the hard disk drive storing a sub-block associated with the error. Once detected, the ECC recovery can be performed locally by the same target processing modules, by a selected one of the target processing modules and/or by the data processing module. 
         [0060]    In  FIGS. 8A and 8B , flowcharts illustrating exemplary methods for retrieving data blocks are shown. In this implementation, the ECC processing for data having ECC errors is performed by the data processing module. In  FIG. 8A , control begins step  320  and proceeds to step  322  where the data processing module determines whether a data retrieval request has been received. If step  322  is true, the data processing module sends a broadcast message to all of the target processing modules having data associated with the data retrieval request in step  324 . Alternately, the data processing module can use the map and send individual messages to each of the target processing modules individually. 
         [0061]    In step  326 , the data processing module determines whether it has received data blocks from the target processing modules with errors (and corresponding ECC data for the data with errors). If step  326  is true, the data processing module uses the ECC data to recover the data. Steps  326  and  327  continue with step  328  where the data processing module sends the corrected data to the requester. If the errors cannot be corrected, the data processing module may send an error message and/or retry retrieval. Control ends in step  329 . 
         [0062]    In  FIG. 8B , control begins with step  330  and proceeds to step  332 . In step  332 , the target processing module determines whether it has received a data retrieval request from the data processing module. In step  334 , the target processing module retrieves and sends data relating to the retrieval request to the data processing module. In step  336 , the target processing module determines whether there are errors detected in a sub-block. If step  336  is true, the target processing module sends the ECC data relating to the sub-block to the data processing module. Steps  336  and  337  continue with step  338  where control determines whether all of the data has been sent relating to the data retrieval request. If not, control returns to step  334 . If step  338  is true, control ends with step  339 . 
         [0063]    In  FIGS. 9A and 9B , flowcharts illustrating exemplary methods for retrieving data blocks are shown. In this implementation, the ECC processing is performed by respective ones of the target processing modules that store the data. In  FIG. 9A , control begins with step  340 . In step  342 , the data processing module determines whether it has received a data retrieval request. If step  342  is true, the data processing module sends a broadcast message to all of the target processing modules in step  334 . Alternately, the data processing module may send individual messages to the target processing modules based on the map. In step  348 , the data processing module receives and forwards the data to the requester. Control ends with step  349 . 
         [0064]    In  FIG. 9B , control begins with step  350 . In step  352 , the target processing module determines whether it has received a data retrieval request. If step  352  is true, the target processing module sends the data relating to the retrieval request in sub-blocks to the data processing module in step  354 . In step  356 , control determines whether errors have been detected in the sub-blocks. If step  356  is true, control continues with step  357  and processes the ECC to recover data and sends the recovered data. If the data cannot be recovered, an error message may be sent and/or retry performed. Control continues from steps  356  and  357  with step  358 . In step  358 , control determines whether all of the sub-blocks associated with the data retrieval request have been sent. If not, control returns to step  354 . Otherwise control ends with step  359 . 
         [0065]    In  FIG. 10 , a flowchart illustrating an exemplary method for retrieving data blocks with ECC processing is shown. In this implementation, data recovery may be performed by a selected one of the target processing modules. Control begins with step  360  and proceeds to step  361 . In step  361 , the data processing module determines whether it has received a data retrieval request. If step  361  is true, the data processing module assigns the data retrieval to one of the target processing modules in step  362 . The selected target processing module and/or the data processing module requests data from the remote target processing modules. 
         [0066]    In step  364 , the remote target processing modules send data sub-blocks relating to the retrieval request to the selected target processing module. Likewise, the selected target processing module retrieves data relating to the retrieval request from local drives. Alternately, the remote target processing modules may send the data directly to the data processing module if there are no errors. If there are errors, the remote target processing modules may send the data to the selected target processing module for data recovery. 
         [0067]    For each of the remote target processing modules, the remote target processing modules determine whether errors have been detected in one of the data sub-blocks in step  366 . If step  366  is true, the remote target processing modules send ECC data associated with the sub-block with errors to the selected target processing module. The data sub-blocks without errors may be sent to the target processing module or the data processing module. 
         [0068]    Control continues from steps  366  and  367  with step  368 . In step  368 , control associated with the remote target processing modules determines whether all of the data sub-blocks have been sent. In step  370 , the selected target processing module to uses the ECC data for data recovery, in other words to correct the errors. The selected target processing module forwards the data to the data processing module. The data processing module forwards the recovered data to the requesting device in step  372 . 
         [0069]    Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, the specification and the following claims.