Abstract:
Briefly, techniques to separate a file system and its related meta-data from associated data stored in a mass storage device and store the meta-data on a low latency random access storage device with approximately uniform access times.

Description:
FIELD  
       [0001]     The subject matter disclosed herein generally relates to techniques for storing meta-data.  
       DESCRIPTION OF RELATED ART  
       [0002]     File systems are well known techniques to manage storage and retrieval of files. Examples file systems include, but are not limited to, Microsoft file allocation table (FAT), Unix, and the Linux file system ext family. File systems typically utilize meta-data. Meta-data may describe the content, quality, condition, and other characteristics of data associated with files. Examples of meta-data include, but are not limited to, directories, file allocation tables, security features, file-names and their linkage, keywords, date-of-creation/modification, author, permissions, and a preview image. Use of a rotating media storage device (e.g., a magnetic storage device) to store meta-data may be inefficient. It is desirable to increase the speed at which meta-data can be retrieved.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0003]      FIG. 1  depicts an embodiment of a system that may use embodiments of the present invention.  
         [0004]      FIG. 2  depicts a block diagram of a system in accordance with an embodiment of the present invention.  
         [0005]      FIG. 3  depicts an example process that can be used to reserve region(s) in a storage device that stores meta-data, in accordance with an embodiment of the present invention.  
         [0006]      FIG. 4  depicts examples of schemes that can be used for address mapping meta-data in a mass storage device and/or meta-data storage device, in accordance with embodiments of the present invention.  
         [0007]      FIG. 5  depicts a process to access data and meta-data, in accordance with embodiments of the present invention.  
         [0008]      FIG. 6  depicts a process to convert a logical block address to a physical address of a meta-data storage device, in accordance with embodiments of the present invention. 
     
    
       [0009]     Note that use of the same reference numbers in different figures indicates the same or like elements.  
       DETAILED DESCRIPTION  
       [0010]      FIG. 1  depicts an embodiment of a system that may use embodiments of the present invention. System  100  may include a central processing unit (CPU)  102 , interface  104 , mass storage device  106 , and meta-data storage device  108 .  
         [0011]     For example, interface  104  may be compatible with, but not limited to, Ten Gigabit Attachment Unit Interface (XAUI) (described in IEEE 802.3, IEEE 802.3ae, and related standards), Ethernet (described in IEEE 802.3 and related standards), Serial Peripheral Interface (SPI), I 2 C, universal serial bus (USB), IEEE 1394, Gigabit Media Independent Interface (GMII) (described in IEEE 802.3, IEEE 802.3ae, and related standards), Peripheral Component Interconnect (PCI) (as well as related standards), ten bit interface (TBI), serial ATA (as well as related standards), and/or parallel ATA (as well as related standards).  
         [0012]     For example, mass storage device  106  may be implemented as any storage device including, but not limited to, a magnetic storage device or an array of magnetic storage devices. In one implementation, mass storage device  106  may store data and also may be used to store meta-data.  
         [0013]     For example, meta-data storage device  108  may be implemented as a storage device with approximately uniform access time for randomly stored information (where the access time may be the time between receipt of a request by meta-data storage device  108  of a read or write operation and completion of such read or write operation). As compared to mass storage device  106 , meta-data storage device  108  may have a lower average access time for randomly stored information. For example, meta-data storage device  108  may be implemented as a non-volatile memory device such as random access memory device (e.g., a DRAM, battery backed-up DRAM, or flash memory). In one implementation, meta-data storage device  108  may store meta-data as well as an associated address mapping table that associates meta-data with storage locations in meta-data storage device  108 . Meta-data storage device  108  may further include storage regions for disk caching, reserved memory for application use, and reserved memory for a solid-state disk drive.  
         [0014]     Storing meta-data in meta-data storage device  108  may provide an improvement over typical file-system operations that access meta-data such as searching for a file by one or more fields in the meta-data (e.g., file-name, date of creation/revision, author name, or version number) or other operations such as directory listings because access times of meta-data may be reduced on average. Searches for files by key words in the content of the file can be accelerated by including such key words in meta-data associated with the file.  
         [0015]      FIG. 2  depicts a block diagram of a system  200  in accordance with an embodiment of the present invention. System  200  may include user program  201 , file system driver  202 , filter driver  204 , mass storage device controller  206 , meta-data storage device controller  208 , mass storage device  106 , and meta-data storage device  108 . User program  201 , file system driver  202 , filter driver  204 , mass storage device controller  206 , and meta-data storage device controller  208  may be implemented as any or a combination of hardwired logic, software stored by a memory device and executed by a microprocessor, firmware, an application specific integrated circuit (ASIC), and/or a field programmable gate array (FPGA).  
         [0016]     User program  201  may attempt to store, retrieve, or perform some other action with respect to files stored in a storage device. To initiate actions with respect to files, user program  201  may provide a file name and/or file path as well as an associated action (e.g., read, write, or seek) to perform for the file.  
         [0017]     In one embodiment, file system driver  202  may determine whether a requested operation accesses meta-data. For example, file system driver  202  may determine what data or meta-data needs to be accessed to satisfy a request from user program  201 . For a meta-data access, an identified storage medium may be meta-data storage device  108  whereas for a data access, the identified storage medium may be mass storage device  106 . For examples of techniques to associate meta-data with a requested file or directory, see publications describing the Microsoft FAT, Linux, and/or Unix.  
         [0018]     In one embodiment, filter driver  204  may transfer to the proper storage device controller a request for meta-data or data based on (1) the identity of the storage medium that stores meta-data or data and (2) a logical block address in the storage medium of the meta-data or data. For example, the storage device controller may be mass storage device controller  206  or meta-data storage device controller  208 . For example, filter driver  204  may determine a logical block address of the meta-data or data based on the file name, file path, and requested action.  
         [0019]     In one embodiment, filter driver  204  may request allocation for meta-data storage in meta-data storage device  108  in response, for example, to a request to access meta-data or a request to allocate meta-data storage in meta-data storage device  108 . To initiate meta-data allocation, filter driver  204  may request meta-data storage controller  208  to reserve a storage region in meta-data storage device  108  for meta-data. For example, to request allocation for meta-data storage in meta-data storage device  108 , the process described with respect to  FIG. 3  may be used, although other techniques may be used.  
         [0020]     Mass storage device controller  206  may manage reading and writing of data within mass storage device  106 . Meta-data storage device controller  208  may reserve region(s) in meta-data storage device  108  for storing meta-data and update the address mapping table. Meta-data storage device controller  208  may modify region(s) reserved in meta-data storage device  108  for storing meta-data as well as update the address mapping table. For example, meta-data storage device controller  208  may designate meta-data for storage in meta-data storage device  108  (mark meta-data as “do not evict”) but allow redundant copies in other storage devices.  
         [0021]      FIG. 3  depicts an example process that can be used to reserve region(s) in meta-data storage device  108  for storing meta-data as well as to update the address mapping table, in accordance with an embodiment of the present invention. The process of  FIG. 3  may be initiated at least in response to a request to initialize reserve region(s) in meta-data storage device  108  or in response to a request to access meta-data that is not stored in meta-data storage device  108 .  
         [0022]     Action  310  may include determining available storage capacity of mass storage device  106  and meta-data storage device  108 . For example, mass storage device controller  206  and meta-data storage device controller  208  may provide available storage capacity of respective mass storage device  106  and meta-data storage device  108 .  
         [0023]     Action  320  may include allocating a region of addressable locations in meta-data storage device  108  for storing meta-data. For example, based on the available storage capacity of mass storage device  106  and meta-data storage device  108 , action  320  may determine a size and type of meta-data that can be stored in meta-data storage device  108 . For example, action  320  may initially allocate table and file system types of meta-data, although other types of meta-data may be allocated based, at least, on the available storage capacity of mass storage device  106  and meta-data storage device  108 .  
         [0024]     For example,  FIG. 4  depicts examples of schemes that can be used for address mapping meta-data in mass storage device  106  and meta-data storage device  108 , in accordance with embodiments of the present invention. In scheme  402 , unique addresses are provided for storing meta-data in meta-data storage device  108  as well as for storing data in mass storage device  106 . In scheme  404 , an address for meta-data may correspond to an addressable storage location in both mass storage device  106  and meta-data storage device  108  so that meta-data may be stored in both mass storage device  106  and meta-data storage device  108 . However, under scheme  404 , in response to requests to access meta-data, meta-data may be accessed from meta-data storage device  108 .  
         [0025]     Action  330  may include formatting the allocated region in the meta-data storage device  108  for meta-data storage in accordance with meta-data specifications, such as Microsoft file allocation table (FAT), Unix, and/or Linux file system ext family, and updating the address mapping table.  
         [0026]      FIG. 5  depicts a process to access data and meta-data, in accordance with embodiments of the present invention. Action  501  may include breaking up a file access request into request portions. For example, the file access request may include request portions to access meta-data and/or data. A request for a file or directory access may be broken down into request portions that are either completely meta-data requests or completely data requests.  
         [0027]     Action  502  may include processing a first request portion included with a file access request. Action  503  may follow action  502 .  
         [0028]     Action  503  may include determining whether any request portions have not been processed. If any request portion has not been processed, action  510  may follow action  503 . If all request portions of the file access request have been processed, action  505  may follow action  503 .  
         [0029]     Action  505  may include returning to the routine that called the process of  FIG. 5 .  
         [0030]     Action  510  may include determining whether a request portion is a request for meta-data. For example, based on the file name, file path, and requested action, the process may determine a logical block address from which to retrieve meta-data or data. Accordingly, in one implementation, action  510  may include determining whether the current request portion is for meta-data based on the logical block address. As illustrated by schemes  402  and  404  ( FIG. 4 ), a range of logical block addresses may correspond to storage locations for meta-data.  
         [0031]     For example, in one implementation, action  510  may utilize a look-up-table that associates file names with associated meta-data storage locations and thereby may determine if a request portion includes a request for meta-data. If the file access request includes a request for meta-data, then action  530  may follow action  510 . If the file access request does not include a request for meta-data, then action  520  may follow action  510 .  
         [0032]     Action  520  may include issuing a request to access data stored at a specified logical block address to mass storage device  106 . For example, action  520  may include iteratively accessing meta-data (e.g., directory structure and file allocation tables) to determine storage location(s) (e.g., logical block address) and a storage medium for the data associated with the file access request.  
         [0033]     Action  530  may include translating a logical block address to a meta-data storage address. For example, action  530  may use the process described with respect to  FIG. 6 , although other techniques may be used. Action  540  may follow action  530 . Action  540  may include issuing a request to access meta-data from a storage location specified in action  530  from meta-data storage device  108 .  
         [0034]      FIG. 6  depicts a process to convert a logical block address to a physical address in a meta-data storage device, in accordance with embodiments of the present invention. Action  610  may include querying a look-up-table that associates logical block addresses with physical addresses in meta-data storage device  108  to determine if the requested logical block address has been allocated in the look-up-table. If the requested logical block address has been allocated in the look-up-table, action  620  may follow action  610 . If the requested logical block address has not been allocated in the look-up-table, action  630  may follow action  610 .  
         [0035]     Action  620  may include providing from the look-up-table a physical address in meta-data storage device  108  associated with the provided logical block address.  
         [0036]     Action  630  may include associating an available physical address in meta-data storage device  108  with the provided logical block address. Action  640  may follow action  630 . Action  640  may include updating the look-up-table to include the association(s) determined in action  630 . Action  650  may follow action  640 . Action  650  may include providing the physical address associated with the provided logical block address.  
         [0037]     The drawings and the forgoing description gave examples of the present invention. While a demarcation between operations of elements in examples herein is provided, operations of one element may be performed by one or more other elements. The scope of the present invention, however, is by no means limited by these specific examples. Numerous variations, whether explicitly given in the specification or not, such as differences in structure, dimension, and use of material, are possible. The scope of the invention is at least as broad as given by the following claims.