Patent Publication Number: US-9430368-B1

Title: System and method for caching data

Description:
TECHNICAL FIELD 
     This disclosure relates to storage devices and, more particularly, to multi-tier storage devices. 
     BACKGROUND 
     Storing and safeguarding electronic content is of paramount importance in modern business. Accordingly, various systems may be employed to protect such electronic content. Data storage system are often compartmentalized into different tiers having different levels of performance, wherein data that is accessed less often is placed into a slower performance tier, while data that is accessed more often is placed into a higher performance tier. 
     SUMMARY OF DISCLOSURE 
     In a first implementation, a computer-implemented method includes processing a read request for a piece of content stored within a storage system. If it is determined that the piece of content is not present within a front end cache system of the storage system, requesting the piece of content from a multi-tiered data array, thus defining requested content. The requested content is received from the multi-tiered data array. A tier designator, concerning the requested content, is received that identifies a specific data tier within the multi-tiered data array from which the requested content was obtained. 
     One or more of the following features may be included. The tier designator may be processed to determine whether the requested content should be written to the front end cache system. The requested content may be written to the front end cache system when the requested content is obtained from slower data tiers within the multi-tiered data array. The requested content may not be written to the front end cache system when the requested content is obtained from faster data tiers within the multi-tiered data array. The multi-tiered data array may include a faster data tier, a medium data tier, and a slower data tier. The faster data tier may include one or more flash storage devices, the medium data tier may include one or more fiber channel storage devices, and the slower data tier may include one or more SATA storage devices. The front end cache system may be a flash-based front end cache system. The multi-tiered data array may include a back end cache system. 
     In another implementation, a computer program product residing on a computer readable medium having a plurality of instructions stored thereon which, when executed by a processor, cause the processor to perform operations including processing a read request for a piece of content stored within a storage system. If it is determined that the piece of content is not present within a front end cache system of the storage system, requesting the piece of content from a multi-tiered data array, thus defining requested content. The requested content is received from the multi-tiered data array. A tier designator, concerning the requested content, is received that identifies a specific data tier within the multi-tiered data array from which the requested content was obtained. 
     One or more of the following features may be included. The tier designator may be processed to determine whether the requested content should be written to the front end cache system. The requested content may be written to the front end cache system when the requested content is obtained from slower data tiers within the multi-tiered data array. The requested content may not be written to the front end cache system when the requested content is obtained from faster data tiers within the multi-tiered data array. The multi-tiered data array may include a faster data tier, a medium data tier, and a slower data tier. The faster data tier may include one or more flash storage devices, the medium data tier may include one or more fiber channel storage devices, and the slower data tier may include one or more SATA storage devices. The front end cache system may be a flash-based front end cache system. The multi-tiered data array may include a back end cache system. 
     In another implementation, a computing system including at least one processor and at least one memory architecture coupled with the at least one processor, wherein the computing system is configured to perform operations including processing a read request for a piece of content stored within a storage system. If it is determined that the piece of content is not present within a front end cache system of the storage system, requesting the piece of content from a multi-tiered data array, thus defining requested content. The requested content is received from the multi-tiered data array. A tier designator, concerning the requested content, is received that identifies a specific data tier within the multi-tiered data array from which the requested content was obtained. 
     One or more of the following features may be included. The tier designator may be processed to determine whether the requested content should be written to the front end cache system. The requested content may be written to the front end cache system when the requested content is obtained from slower data tiers within the multi-tiered data array. The requested content may not be written to the front end cache system when the requested content is obtained from faster data tiers within the multi-tiered data array. The multi-tiered data array may include a faster data tier, a medium data tier, and a slower data tier. The faster data tier may include one or more flash storage devices, the medium data tier may include one or more fiber channel storage devices, and the slower data tier may include one or more SATA storage devices. The front end cache system may be a flash-based front end cache system. The multi-tiered data array may include a back end cache system. 
     The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features and advantages will become apparent from the description, the drawings, and the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagrammatic view of a storage system and a data caching process coupled to a distributed computing network; 
         FIG. 2  is a diagrammatic view of the storage system of  FIG. 1 ; and 
         FIG. 3  is a flow chart of the data caching process of  FIG. 1 . 
     
    
    
     Like reference symbols in the various drawings indicate like elements. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     System Overview: 
     Referring to  FIG. 1 , there is shown data caching process  10  that may reside on and may be executed by storage system  12 , which may be connected to network  14  (e.g., the Internet or a local area network). Examples of storage system  12  may include, but are not limited to: a Network Attached Storage (NAS) system, a Storage Area Network (SAN), a personal computer with a memory system, a server computer with a memory system, and a cloud-based device with a memory system. 
     As is known in the art, a SAN may include one or more of a personal computer, a server computer, a series of server computers, a mini computer, a mainframe computer, a RAID device and a NAS system. The various components of storage system  12  may execute one or more operating systems, examples of which may include but are not limited to: Microsoft Windows XP Server™; Novell Netware™; Redhat Linux™, Unix, or a custom operating system, for example. 
     The instruction sets and subroutines of data caching process  10 , which may be stored on storage device  16  included within storage system  12 , may be executed by one or more processors (not shown) and one or more memory architectures (not shown) included within storage system  12 . Storage device  16  may include but is not limited to: a hard disk drive; a tape drive; an optical drive; a RAID device; a random access memory (RAM); a read-only memory (ROM); and all forms of flash memory storage devices. 
     Network  14  may be connected to one or more secondary networks (e.g., network  18 ), examples of which may include but are not limited to: a local area network; a wide area network; or an intranet, for example. 
     Various data requests (e.g. data request  20 ) may be sent from client applications  22 ,  24 ,  26 ,  28  to storage system  12 . Examples of data request  20  may include but are not limited to data write requests (i.e. a request that content be written to storage system  12 ) and data read requests (i.e. a request that content be read from storage system  12 ). 
     The instruction sets and subroutines of client applications  22 ,  24 ,  26 ,  28 , which may be stored on storage devices  30 ,  32 ,  34 ,  36  (respectively) coupled to client electronic devices  38 ,  40 ,  42 ,  44  (respectively), may be executed by one or more processors (not shown) and one or more memory architectures (not shown) incorporated into client electronic devices  38 ,  40 ,  42 ,  44  (respectively). Storage devices  30 ,  32 ,  34 ,  36  may include but are not limited to: hard disk drives; tape drives; optical drives; RAID devices; random access memories (RAM); read-only memories (ROM), and all forms of flash memory storage devices. Examples of client electronic devices  38 ,  40 ,  42 ,  44  may include, but are not limited to, personal computer  38 , laptop computer  40 , personal digital assistant  42 , notebook computer  44 , a server (not shown), a data-enabled, cellular telephone (not shown), and a dedicated network device (not shown). 
     Client electronic devices  38 ,  40 ,  42 ,  44  may each execute an operating system, examples of which may include but are not limited to Microsoft Windows™, Microsoft Windows CE™, Redhat Linux™, or a custom operating system. 
     Users  46 ,  48 ,  50 ,  52  may access storage system  12  directly through network  14  or through secondary network  18 . Further, storage system  12  may be connected to network  14  through secondary network  18 , as illustrated with link line  54 . 
     The various client electronic devices may be directly or indirectly coupled to network  14  (or network  18 ). For example, personal computer  38  is shown directly coupled to network  14  via a hardwired network connection. Further, notebook computer  44  is shown directly coupled to network  18  via a hardwired network connection. Laptop computer  40  is shown wirelessly coupled to network  14  via wireless communication channel  56  established between laptop computer  40  and wireless access point (i.e., WAP)  58 , which is shown directly coupled to network  14 . WAP 58 may be, for example, an IEEE 802.11a, 802.11b, 802.11g, 802.11n, Wi-Fi, and/or Bluetooth device that is capable of establishing wireless communication channel  56  between laptop computer  40  and WAP 58. Personal digital assistant  42  is shown wirelessly coupled to network  14  via wireless communication channel  60  established between personal digital assistant  42  and cellular network/bridge  62 , which is shown directly coupled to network  14 . 
     For the following discussion, client application  22  is going to be described for illustrative purposes. However, this is not intended to be a limitation of this disclosure, as other client applications (e.g., client applications  24 ,  26 ,  28 ) may be equally utilized. 
     For illustrative purposes, storage system  12  will be described as being a network-based storage system that includes a plurality of rotating, electro-mechanical backend storage devices. However, this is for illustrative purposes only and is not intended to be a limitation of this disclosure, as other configurations are possible and are considered to be within the scope of this disclosure. For example and as discussed above, storage system  12  may be a personal computer that includes a single electro-mechanical storage device. 
     Referring also to  FIG. 2 , storage system  12  may include a server computer/controller (e.g. server computer/controller  100 ), and a plurality of data tiers T  1 - n  (e.g. data tiers  102 ,  104 ,  106 ). Data tiers  102 ,  104 ,  106  may be configured to provide various levels of performance. For example. one or more of data tiers  102 ,  104 ,  106  may be configured to be a lower performance data tier and one or more of data tiers  102 ,  104 ,  106  may be configured to be a higher performance data tier. 
     For example, data tier  102  may be configured as a higher performance data tier and may include one or more flash storage devices. Data tier  104  may be configured as a medium performance data tier and may include one or more fiber channel storage devices. And data tier  106  may be configured as a lower performance data tier and may include one or more lower performance storage devices (e.g., SATA drives, SCSI drives, SAS drives, IDE drives, and EIDE drives). 
     One or more of data tiers  102 ,  104 ,  106  may be configured to provide various levels of performance and/or high availability. For example, one or more of data tiers  102 ,  104 ,  106  may be configured as a RAID 0 array, in which data is striped across multiple drives. By striping data across multiple drives, improved performance may be realized. However, RAID 0 arrays do not provide a level of high availability. Accordingly, one or more of data tiers  102 ,  104 ,  106  may be configured as a RAID 1 array, in which data is mirrored between multiple drives. By mirroring data between multiple drives, a level of high availability is achieved as multiple copies of the data are stored within storage system  12 . 
     While data tiers  102 ,  104 ,  106  are discussed above as possibly being configured in a RAID 0 or RAID 1 array, this is for illustrative purposes only and is not intended to be a limitation of this disclosure, as other configurations are possible. For example, data tiers  102 ,  104 ,  106  may be configured in a non-RAID fashion or as a RAID 3, RAID 4, RAID 5 or RAID 6 array. 
     While in this particular example, storage system  12  is shown to include three data tiers (e.g. data tiers  102 ,  104 ,  106 ), this is for illustrative purposes only and is not intended to be a limitation of this disclosure. Specifically, the actual number of data tiers may be increased or decreased depending upon system needs. 
     As discussed above, data tiers  102 ,  104 ,  106  may include one or more one or more flash storage devices, fiber channel storage devices, and lower performance storage devices (e.g., SATA drives, SCSI drives, SAS drives, IDE drives, and EIDE drives). 
     Storage system  12  may execute all or a portion of data caching process  10 . The instruction sets and subroutines of data caching process  10 , which may be stored on a storage device (e.g., storage device  16 ) coupled to server computer/controller  100 , may be executed by one or more processors (not shown) and one or more memory architectures (not shown) included within server computer/controller  100 . Storage device  16  may include but is not limited to: a hard disk drive; a tape drive; an optical drive; a RAID device; a random access memory (RAM); a read-only memory (ROM); and all forms of flash memory storage devices. 
     As discussed above, various data requests (e.g. data request  20 ) may be generated. For example, these data requests may be sent from client applications  22 ,  24 ,  26 ,  28  to storage system  12 . Additionally/alternatively and when server computer/controller  100  is configured as an application server, these data requests may be internally generated within server computer/controller  100 . Examples of data request  20  may include but are not limited to data write request  108  (i.e. a request that content  110  be written to storage system  12 ) and data read request  112  (i.e. a request that content  110  be read from storage system  12 ). 
     Server computer/controller  100  may include input-output logic  114  (e.g., a network interface card or a Host Bus Adaptor (HBA)), processing logic  116 , and first cache system  118 . Examples of first cache system  118  may include but are not limited to a volatile, solid-state, cache memory system (e.g., a dynamic RAM cache memory system) and/or a non-volatile, solid-state, cache memory system (e.g., a flash-based, cache memory system). 
     During operation of server computer/controller  100 , content  110  to be written to storage system  12  may be received by input-output logic  114  (e.g. from network  14  and/or network  18 ) and processed by processing logic  116 . Additionally/alternatively and when server computer/controller  100  is configured as an application server, content  110  to be written to storage system  12  may be internally generated by server computer/controller  100 . As will be discussed below in greater detail, processing logic  116  may initially store content  110  within first cache system  118 . 
     Depending on the manner in which first cache system  118  is configured, processing logic  116  may immediately write content  110  to second cache system  120 /data tiers  102 ,  104 ,  106  (if first cache system  118  is configured as a write-through cache) or may subsequently write content  110  to second cache system  120 /data tiers  102 ,  104 ,  106  (if first cache system  118  is configured as a write-back cache). Examples of second cache system  120  (i.e., a backend cache system) may include but are not limited to a volatile, solid-state, cache memory system (e.g., a dynamic RAM cache memory system) and/or a non-volatile, solid-state, cache memory system (e.g., a flash-based, cache memory system). 
     The combination of second cache system  120  and data tiers  102 ,  104 ,  106  may form data array  122 , wherein first cache system  118  may be sized so that the number of times that data array  122  is accessed may be reduced. Accordingly, by sizing first cache system  118  so that first cache system  118  retains a quantity of data sufficient to satisfy a significant quantity of data requests (e.g., data request  20 ), the overall performance of storage system  12  may be enhanced. 
     Further, second cache system  120  within data array  122  may be sized so that the number of times that data tiers  102 ,  104 ,  106  are accessed may be reduced. Accordingly, by sizing second cache system  120  so that second cache system  120  retains a quantity of data sufficient to satisfy a significant quantity of data requests (e.g., data request  20 ), the overall performance of storage system  12  may be enhanced. 
     As discussed above, the instruction sets and subroutines of data caching process  10 , which may be stored on storage device  16  included within storage system  12 , may be executed by one or more processors (not shown) and one or more memory architectures (not shown) included within storage system  12 . Accordingly, in addition to being executed on server computer/controller  100 , some or all of the instruction sets and subroutines of data caching process  10  may be executed by one or more processors (not shown) and one or more memory architectures (not shown) included within data array  122 . 
     The Data Caching Process 
     As discussed above, data tiers  102 ,  104 ,  106  may be configured to provide various levels of performance, wherein one or more of data tiers  102 ,  104 ,  106  may be configured to be a lower performance data tier and one or more of data tiers  102 ,  104 ,  106  may be configured to be a higher performance data tier. 
     Accordingly, data tier  102  may be configured as a higher performance data tier and may include one or more flash storage devices. Data tier  104  may be configured as a medium performance data tier and may include one or more fiber channel storage devices. And data tier  106  may be configured as a lower performance data tier and may include one or more lower performance storage devices (e.g., SATA drives, SCSI drives, SAS drives, IDE drives, and EIDE drives). 
     Assume for illustrative purposes that data caching process  10  receives read request  112  for content  110 , which is a very old piece of content stored within storage system  12 . For example, assume that a customer of a cellular provider contacts the cellular provider to obtain a copy of a phone bill (i.e., content  110 ) that is over two years old. Data caching process  10  may process  200  read request  112  for content  110  stored within storage system  12 . 
     Data caching process  10  may first determine whether content  110  is present within a front end cache system (e.g., first cache system  118 ). If so, data caching process  10  may obtain content  110  from first cache system  118  and provide the same to the requestor, thus satisfying read request  112 . If data caching process  10  determines  202  that content  110  is not present within the front end cache system (e.g., first cache system  118 ) of storage system  12 , data caching process  10  may request  204  content  110  from data array  122  (i.e., a multi-tiered data array), thus defining requested content  124 . 
     Data array  122  may obtain requested content  124  from one of the data tiers (e.g., data tiers  102 ,  104 ,  106 ) included within data array  122  and provide requested content  124  to data caching process  10 . Data array  122  may generate tier designator  126  that may define the specific data tier within data array  122  from which requested content  124  was obtained. For example, since requested content  124  is quite old, it is likely that requested content  124  would be stored within a slower data tier. For illustrative purpose, assume that requested content  124  was obtained from data tier  106 , which would be identified in tier designator  126 . 
     Data caching process  10  may receive  206  requested content  124  from multi-tiered data array  122 . Additionally, data caching process  10  may also receive  208  tier designator  126  (which concerns and is associated with requested content  124 ) that identifies the specific data tier (e.g., data tier  106 ) within data array  122  from which requested content  124  was obtained. 
     Data caching process  10  may process  210  tier designator  126  to determine whether requested content  124  should be written to the front end cache system (e.g., first cache system  118 ). Specifically, data caching process  10  may write  212  requested content  124  to the front end cache system (e.g., first cache system  118 ) when requested content  124  was obtained from slower data tiers within data array  122 . Conversely, data caching process  10  may not write  214  requested content  124  to the front end cache system (e.g., first cache system  118 ) when requested content  124  was obtained from faster data tiers within data array  122 . 
     For example, assume that data caching process  10  is configure to store requested content  124  only when requested content  124  is not from the fastest data tier (namely data tier  102 ). Therefore, upon receiving  206  requested content  124  and receiving  208  tier designator  126 , both from multi-tiered data array  122 , data caching process  10  may process  210  tier designator  126 . Accordingly, if requested content  124  is from data tier  106  or data tier  104 , data caching process  10  may store  212  requested content  124  within the front end cache system (e.g., first cache system  118 ). Conversely. if requested content  124  is from data tier  102 , data caching process  10  may not store  214  requested content  124  within the front end cache system (e.g., first cache system  118 ). Since (in this example), requested content is quite old and was stored within the slowest data tier (i.e., data tier  106 ), data caching process  10  may store  212  requested content  124  within the front end cache system (e.g., first cache system  118 ). 
     General 
     As will be appreciated by one skilled in the art, the present disclosure may be embodied as a method, a system, or a computer program product. Accordingly, the present disclosure may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “circuit,” “module” or “system.” Furthermore, the present disclosure may take the form of a computer program product on a computer-usable storage medium having computer-usable program code embodied in the medium. 
     Any suitable computer usable or computer readable medium may be utilized. The computer-usable or computer-readable medium may be, for example but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, device, or propagation medium. More specific examples (a non-exhaustive list) of the computer-readable medium may include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a transmission media such as those supporting the Internet or an intranet, or a magnetic storage device. The computer-usable or computer-readable medium may also be paper or another suitable medium upon which the program is printed, as the program can be electronically captured, via, for instance, optical scanning of the paper or other medium, then compiled, interpreted, or otherwise processed in a suitable manner, if necessary, and then stored in a computer memory. In the context of this document, a computer-usable or computer-readable medium may be any medium that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. The computer-usable medium may include a propagated data signal with the computer-usable program code embodied therewith, either in baseband or as part of a carrier wave. The computer usable program code may be transmitted using any appropriate medium, including but not limited to the Internet, wireline, optical fiber cable, RF, etc. 
     Computer program code for carrying out operations of the present disclosure may be written in an object oriented programming language such as Java, Smalltalk, C++ or the like. However, the computer program code for carrying out operations of the present disclosure may also be written in conventional procedural programming languages, such as the “C” programming language or similar programming languages. The program code may execute entirely on the user&#39;s computer, partly on the user&#39;s computer, as a stand-alone software package, partly on the user&#39;s computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user&#39;s computer through a local area network/a wide area network/the Internet (e.g., network  14 ). 
     The present disclosure is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the disclosure. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, may be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer/special purpose computer/other programmable data processing apparatus, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. 
     These computer program instructions may also be stored in a computer-readable memory that may direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function/act specified in the flowchart and/or block diagram block or blocks. 
     The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. 
     The flowcharts and block diagrams in the figures may illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments of the present disclosure. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustrations, and combinations of blocks in the block diagrams and/or flowchart illustrations, may be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present disclosure has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the disclosure in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the disclosure. The embodiment was chosen and described in order to best explain the principles of the disclosure and the practical application, and to enable others of ordinary skill in the art to understand the disclosure for various embodiments with various modifications as are suited to the particular use contemplated. 
     A number of implementations have been described. Having thus described the disclosure of the present application in detail and by reference to embodiments thereof, it will be apparent that modifications and variations are possible without departing from the scope of the disclosure defined in the appended claims.