Patent Publication Number: US-11392545-B1

Title: Tracking access pattern of inodes and pre-fetching inodes

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present patent application is a continuation of U.S. patent application Ser. No. 15/279,694, filed on Sep. 29, 2016, entitled “Tracking Access Pattern of Modes and Pre-Fetching Modes,” and having Bhautik Patel, Freddy James, Mitul Kothari, and Anindya Banerjee as inventors, which is incorporated by reference herein, in its entirety and for all purposes. 
    
    
     FIELD OF THE DISCLOSURE 
     This disclosure relates to data access. In particular, this disclosure relates to tracking access patterns of inodes, and issuing inode read-ahead instructions to pre-fetch inodes. 
     DESCRIPTION OF THE RELATED ART 
     A file system is used to control how data is stored and retrieved for computing purposes (e.g., for storing and executing applications). A data object in a file system (e.g., a file, a directory, or the like) has one or more inodes. An inode is a data structure that is used to identify data belonging to the data object in the file system. The inode stores attributes (e.g., metadata) and disk block location(s) of the data object&#39;s data. 
     Accessing a file in a file system requires the file&#39;s inode to be read from disk (e.g., from a non-volatile storage unit). Data operations such as backup, periodic scans, administrative operations, and the like, typically access multiple inodes on disk. Reading such “on-disk” inodes from disk can negatively impact application performance. For example, if the underlying disk is slow, reading on-disk inodes from disk can result in unreasonable and/or significant input/output (I/O) wait time before an application can be serviced with the required data. 
     A file&#39;s contents can be loaded into memory (e.g., Random Access Memory (RAM)) such that when the file is subsequently accessed, the file&#39;s contents are read from RAM rather than from disk (e.g., a Hard Disk Drive (HDD)). However, loading a file&#39;s contents into memory requires inodes that correspond to the file&#39;s contents to be accessed from disk. 
     SUMMARY OF THE DISCLOSURE 
     The present disclosure describes methods, computer program products, computer systems, and the like that provide for the tracking of access patterns of inodes, and the issuing of inode read-ahead instructions, in order to pre-fetch inodes. Such a method can include, for example, identifying a unit of metadata in a file system, identifying a file system structure in the file system, determining whether a file structure of the file system structure is non-sequential, and, in response to a determination that the file structure is non-sequential, retrieving a list of units of metadata. In such embodiments, the file system structure is associated with the unit of metadata, and the determining includes accessing the file system structure. Further, in certain embodiments, the units of metadata identified in the list of units of metadata are stored in a storage device of the computer system. 
     The foregoing is a summary and thus contains, by necessity, simplifications, generalizations and omissions of detail; consequently those skilled in the art will appreciate that the summary is illustrative only and is not intended to be in any limiting. Other aspects, inventive features, and advantages of the present disclosure, as defined solely by the claims, will become apparent in the non-limiting detailed description set forth below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure may be better understood, and its numerous objects, features and advantages made apparent to those skilled in the art by referencing the accompanying drawings. 
         FIG. 1A  is a block diagram of a system that tracks the access pattern of inodes and pre-fetches inodes, according to one embodiment of the present disclosure. 
         FIG. 1B  is a block diagram of a structural file, according to one embodiment of the present disclosure. 
         FIG. 1C  is a block diagram of a structural file and an in-core inode, according to one embodiment of the present disclosure. 
         FIG. 2A  is a block diagram of a system that tracks access patterns of inodes and issues metadata read-ahead instructions, according to one embodiment of the present disclosure. 
         FIG. 2B  is a block diagram of offset metadata of inodes, according to one embodiment of the present disclosure. 
         FIG. 2C  is a table illustrating the contents of a global inode list/parent directory list, according to one embodiment of the present disclosure. 
         FIG. 2D  is a block diagram of a directory access tracker, according to one embodiment of the present disclosure. 
         FIG. 2E  is a block diagram of a metadata read-ahead generator, according to one embodiment of the present disclosure. 
         FIG. 3A  is a block diagram of a directory with sequential inodes, according to one embodiment of the present disclosure. 
         FIG. 3B  is a block diagram of a directory with non-sequential inodes, according to one embodiment of the present disclosure. 
         FIG. 3C  is a block diagram of a cache that implements a global inode list, according to one embodiment of the present disclosure. 
         FIG. 4A  is a flowchart that illustrates a process for performing inode pre-fetching, according to one embodiment of the present disclosure. 
         FIG. 4B  is a flowchart that illustrates a process for storing offset metadata associated with on-disk inodes, according to one embodiment of the present disclosure. 
         FIG. 5A  is a flowchart that illustrates a process for determining the file structure of a directory, according to one embodiment of the present disclosure. 
         FIG. 5B  is a flowchart that illustrates a process for issuing a metadata read-ahead instruction for on-disk inodes, according to one embodiment of the present disclosure. 
         FIG. 6A  is a flowchart that illustrates a process for processing input/output (I/O) operations related to inode pre-fetching, according to one embodiment of the present disclosure. 
         FIG. 6B  is a flowchart that illustrates a process for processing I/O operations, related to inode pre-fetching, according to one embodiment of the present disclosure. 
         FIG. 7A  is a flowchart that illustrates a process for processing access of on-disk inodes, according to one embodiment of the present disclosure. 
         FIG. 7B  is a flowchart that illustrates a process for processing a request to access on-disk inodes, according to one embodiment of the present disclosure. 
         FIG. 8  is a block diagram of a computing system, illustrating how an access pattern tracker and a metadata read-ahead generator can be implemented in software, according to one embodiment of the present disclosure. 
         FIG. 9  is a block diagram of a networked system, illustrating how various computing devices can communicate via a network, according to one embodiment of the present disclosure. 
     
    
    
     While the disclosure is susceptible to various modifications and alternative forms, specific embodiments of the disclosure are provided as examples in the drawings and detailed description. It should be understood that the drawings and detailed description are not intended to limit the disclosure to the particular form disclosed. Instead, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the disclosure as defined by the appended claims. 
     DETAILED DESCRIPTION 
     Introduction 
     A file system (e.g., a Unix file system) is used to organize data and control how that data is stored and retrieved. A file system is responsible for organizing data objects such as files and directories, and for keeping track of which areas of a storage device (e.g., a Hard Disk Drive (HDD), a Solid State Drive (SSD), and/or the like) belong to which data objects. Typically, each data object in a file system (e.g., a file, a directory, or the like) has a corresponding inode. 
     An inode is a data structure used to locate data in a file system. An inode stores attributes (e.g., metadata) and disk block location(s) of the data object&#39;s data, and can be identified by an integer number (e.g., called an inode number). Directories can include lists of names assigned to inodes. A directory contains an entry for itself, an entry for the directory&#39;s parent, and entries for each of the directory&#39;s children. 
     Accessing a file in a file system typically involves the file&#39;s inode to be read from disk (e.g., from a non-volatile storage unit), for example, to determine changes and/or modifications to the file&#39;s contents, and in certain cases, also to verify owner and permission information (e.g., group-id, user-id, permissions, and the like). Therefore, before a file&#39;s contents can be accessed, the file&#39;s inode (metadata) has to be first read from disk. 
     Data operations (e.g., input/output (I/O) operations) typically require the access of multiple inodes on disk, and reading such “on-disk” inodes from disk can negatively impact application performance (e.g., in the form of I/O wait time before a given I/O operation can be completed). Also as previously noted, a file&#39;s contents can be “read-ahead” and loaded into memory (e.g., Random Access Memory (RAM)) such that when the file is subsequently accessed, the file&#39;s contents are read from RAM rather than from disk (e.g., HDD). Therefore, pre-fetching data in this manner (e.g., to accelerate data access) requires tracking of access pattern(s) of inodes to “read-ahead” these inodes, before data associated with those inodes (e.g., files, directories, and the like) can be preemptively loaded into memory. 
     Unfortunately, unlike file data, the efficient tracking of inode metadata access pattern(s) is challenging because of at least two reasons. First, multiple I/O operations (e.g., from multiple applications executing in a cluster) can access the same inode simultaneously. Tracking the inode access pattern(s) of multiple I/O operations can be memory and computing resource intensive, and can result in significant overhead. Second, the tracking of inode access pattern(s) also requires the efficient “read-ahead” of such inodes (e.g., by issuing read-ahead instructions), also without negatively impacting system performance. 
     Disclosed herein are methods, systems, and processes capable of tracking access patterns of inodes based on chunk access, sequential access, and non-sequential access, and issuing read-ahead instructions for inodes, among other capabilities. 
     Example System that Tracks Inode Access Pattern(s) and Issues Read-Ahead 
       FIG. 1A  is a block diagram of a computing system  100 A that is configured to track the access pattern(s) of inodes and pre-fetch inodes, according to one embodiment. As shown in  FIG. 1A , computing device  105  includes a processor  110  and a memory  115 . Computing device  105  can be any type of computing system including a server, a desktop, a laptop, a tablet, and the like, and is communicatively coupled to storage system  145  via network  185 . Network  185  can be any type of network and/or interconnection (e.g., a Local Area Network (LAN), a Wide Area Network (WAN), a Storage Area Network (SAN), the Internet, and the like). 
     Storage system  145  can include a variety of different storage devices, including hard disks, compact discs, digital versatile discs, SSD memory such as Flash memory, and the like, or one or more logical storage devices such as volumes implemented on one or more such physical storage devices. Storage system  145  includes one or more of such storage devices (e.g., disk  150 ). In one embodiment, disk  150  is a non-volatile storage unit. In other embodiments, disk  150  is a HDD or a SSD. Disk  150  includes file system  155 . File system  155  can be any type of file system (e.g., a Unix file system, an extent-based file system, and the like). 
     An operating system  120 , and applications  135  and  140  are stored in memory  115 , and executed by operating system  120 . Operating system  120  further includes an in-core inode list  125  (e.g., with multiple in-core inodes  126 ( 1 )-(N)), including directory inodes  130 ( 1 )-(N). Directory inodes  130 ( 1 )-(N) are parent directory representations of on-disk inodes in in-core mode list  125 , for example (which includes in-core inodes for files, directories, and the like). File system  155  includes a structural file  160 , a directory data structure  170 , and data  180 . Structural file  160  includes on-disk inodes  165 ( 1 )-(N), and directory data structure  170  includes an inode list  175 . In one embodiment, structural file  160  is an iList file. In this embodiment, the iList file is a file that maintains a listing of on-disk inodes (e.g., on-disk inodes  165 ( 1 )-(N)). 
     Data objects (e.g., a file, a directory, and/or the like) in file system  155  are associated with corresponding inodes (e.g., on-disk inodes  165 ( 1 )-(N)). Each on-disk inode has a specific inode number and is stored on disk  150  (e.g., as on-disk inodes  165 ( 1 )-(N), and as part of structural file  160 ). In-core inode list  125  is an in-memory data structure (or list) for one (or more) on-disk inodes. In-core inode list  125  includes the metadata that is stored as part of on-disk inodes  165 ( 1 )-(N), as well as other additional metadata. 
     File system  155  includes directory data structure  170 . Directory data structure  170  includes inode list  175 . The parent of a data object (e.g., a file, a sub-directory, or the like), is a directory of which the given data object is part of. For example, if a given directory (e.g., /home/john) contains four data objects (e.g., file1, file2, file3, and dir1 with pathnames /home/john/file1, /home/john/file2, /home/john/file3, and/home/john/dir1, respectively), then the parent directory of these directory entries (e.g., file1, file2, file3, and dir1) is “john.” Each data object also has a corresponding and/or associated on-disk inode (e.g., on-disk inode  165 ( 1 ) for “john,” on-disk inode  165 ( 2 ) for “file1,” on-disk inode  165 ( 3 ) for “file2,” and on-disk inode  165 ( 4 ) for “file3,” and on-disk inode  165 ( 5 ) for “did”). In this scenario, the parent (directory) inode number of on-disk inodes  165 ( 2 ),  165 ( 3 ),  165 ( 4 ), and  165 ( 5 ) is on-disk inode  165 ( 1 ) (shown as directory inode  130 ( 1 ) in in-core inode list  125  for clarity). 
       FIG. 1B  is a block diagram  100 B of a structural file, and  FIG. 1C  is a block diagram  100 C of structural files and in-core inodes, according to some embodiments. A directory in file system  155  includes a list of tuples (e.g., &lt;file name, inode number of the file&gt;). Inode list  175  is one example of such a list of tuples in file system  155 . The data portion of on-disk inode  165 ( 1 ) includes &lt;file1, on-disk inode  165 ( 2 )&gt;, &lt;file2, on-disk inode  165 ( 3 )&gt;, &lt;file3, on-disk inode  165 ( 4 )&gt;, and &lt;dir1, on-disk inode  165 ( 5 )&gt;. As shown in  FIG. 1B , these “on-disk” inodes are maintained as data of structural file  160  (e.g., an iList file). Because structural file  160  is also a file, structural file  160  also has its own inode with a unique inode number. As shown in  FIG. 1C , when structural file  160 ( 1 ) is brought in-core (e.g., into memory  115 ), an in-core inode is created for structural file  160 ( 1 ) (e.g., in-core inode  126 ( 1 ) in an in-core inode list such as in-core inode list  125 ). Each structural file and on-disk inode has an associated in-core inode. 
       FIG. 2A  is a block diagram of a computing system  200 A that tracks access patterns of inodes and issues metadata read-ahead instructions, according to one embodiment. As shown in  FIG. 2A , computing device  105  includes memory  115 . Memory  115  implements a cache  205 , an access pattern tracker  225 , and a metadata read-ahead generator  240 . Cache  205  implements global inode list  215 , which includes one or more entries from in-core inode list. In-core inode  126 ( 1 ) is an in-memory data structure (or list) that is created for structural file  160 ( 1 ). 
     In-core inode  126 ( 1 ) includes offset metadata  210 . Global inode list  215  is a global in-memory inode list. Offset metadata  210  includes location information of on-disk inode access patterns, and global inode list  215  (also called parent directory list) includes directory inodes  130 ( 1 )-(N) (e.g., in-core parent directory inode numbers of on-disk inodes) and sequential flags  220 ( 1 )-(N). Sequential flags  220 ( 1 )-(N) can be stored as part of in-core inodes for parent directories (e.g., parent directories identified in memory by in-core parent directory inode numbers and shown as directory inodes  130 ( 1 )-(N) in  FIG. 2A ). Access pattern tracker  225  includes a chunk access tracker  230  (e.g., to track chunk access of on-disk inodes), and a directory access tracker (e.g., to track sequential and non-sequential access of on-disk inodes in directories). The foregoing elements of  FIG. 2A  are described in greater detail in connection with  FIGS. 2B-2E . 
     Example of Tracking Chunk Access Pattern of Modes 
       FIG. 2B  is a block diagram  200 B of offset metadata, according to one embodiment. Offset metadata  210  includes an end offset of a last read metadata chunk  245  and a starting offset of a current metadata read operation  250 . Because file system  155  persistently stores in-core inodes  165 ( 1 )-(N) on disk  150 , when a particular inode is not found in-core (e.g., in cache  205 ), chunk access tracker  230 , which is part of access pattern tracker  225 , reads on-disk inodes in structural file  160  from disk  150  in chunks (e.g., 1 KB, 2 KB, 4 KB, or other appropriate size). In this manner, chunk access tracker  230  can be configured to track access patterns of chunks of metadata (e.g., on-disk inodes), and facilitate a determination as to whether an application (e.g., application  135  or application  140 ) is accessing on-disk inodes in a sequential (or nearly-sequential) manner. 
     In one embodiment, chunk access tracker  230  determines a location of a unit of metadata (e.g., the location/end offset of a 1 KB chunk of on-disk inodes  165 ( 1 )-( 4 ) as shown in  FIG. 1B ), in a metadata storage area (e.g., in structural file  160 ). Chunk access tracker  230  determines another location (e.g., a starting offset) in the metadata storage area (e.g., in structural file  160 ) that corresponds to a current metadata read operation. Metadata read-ahead generator  240  then determines whether a metadata read-ahead operation is needed using the location of the data chunk and the another location that corresponds to the current metadata read operation. If the metadata read-ahead operation is needed, metadata read-ahead generator  240  issues the metadata read-ahead operation. 
     Chunk access tracker  230  maintains the end offset of the last read metadata chunk  245  from disk  150  in in-core inode  126 ( 1 ) associated with structural file  160 ( 1 ) (e.g., the end of a logical offset in structural file  160 ( 1 )). For example, if application  135  and/or application  140  attempt to access data  180  in disk  150  that causes (and requires) the reading of a 1 KB chunk of on-disk inodes, then chunk access tracker  230  stores the end offset of the 1 KB chunk of on-disk inodes (e.g., the end offset of the 1 KB chunk of on-disk inode  165 ( 1 )-( 4 ) as shown in  FIG. 1B ) in in-core inode  126 ( 1 ) of structural file  160 ( 1 ) as a “stored value.” 
     In some embodiments, if the starting offset of the current metadata read operation  250  (e.g., on-disk inode  165 ( 5 ) as shown in  FIG. 1B ) is adjacent to the stored value (e.g., the end offset of on-disk inodes  165 ( 1 )-( 4 )—the end offset of the last read metadata chunk  245 ), metadata read-ahead generator  240  issues a metadata read-ahead instruction to fetch the on-disk inodes from 1 KB to 2 KB in structural file  160  (e.g., on-disk inodes  165 ( 5 )-( 8 ) as shown in  FIG. 1B ) into cache  205 . Because chunk access tracker  230  determines that on-disk inode access is happening in a sequential manner, metadata read-ahead generator  240  issues a metadata read-ahead instruction to fetch the next 1 KB chunk of on-disk inodes from disk  150  to in-core inode list  125  (e.g., 1 KB to 2 KB), thus accelerating (future) inode access. 
     If the metadata read-ahead instruction described above is triggered (e.g., if the starting offset of the current metadata read operation  250  is next to the end offset of the last read metadata chunk  245 ), then access pattern tracker  225  updates the stored value (e.g., the end offset of on-disk inodes  165 ( 1 )-( 4 )—the end offset of the last read metadata chunk  245 ) in in-core inode list  125  by replacing the stored value in cache  205  with another end offset of another last read metadata chunk, read by the metadata read-ahead operation (e.g., the end offset of on-disk inodes  165 ( 5 )-( 8 ) (e.g., at 2 KB) as shown in  FIG. 1B , because the metadata read-ahead operation reads ahead on-disk inodes from 1 KB to 2 KB as a result of the (issued) metadata read-ahead instruction). However, if the starting offset of the current metadata read operation  250  is not next to the end offset of the last read metadata chunk  245 , and thus no metadata read-ahead is triggered, access pattern tracker  225  resets the stored value (e.g., the end offset of on-disk inodes  165 ( 1 )-( 4 )—the end offset of the last read metadata chunk  245 ) with an end offset of the current metadata read operation. 
     It will be appreciated that chunk access pattern(s) of inodes can be tracked and metadata read-ahead instructions and/or metadata read-ahead operations can be issued to pre-fetch applicable inodes from disk into memory to accelerate the subsequent access of these inodes. Described next are methods, systems, and processes to track inode access pattern(s) for inodes that are part of directories. 
     Example of Using a Parent Directory List to Track Access Pattern of Modes 
     It will be appreciated that an inode allocation policy can maintain on-disk inodes in proximity to each other within the same directory, referred to herein as proximate locality. For example, the on-disk inodes of files that are accessed frequently and together can be maintained within the same directory. This proximate locality of on-disk inodes in directories can be used to track directory access of inodes. For example, global inode list  215  (or parent directory list) can be created and maintained to track access of on-disk inodes. 
       FIG. 2C  is a table  200 C illustrating the contents of such a global inode list, and  FIG. 2D  is a block diagram  200 D of directory access tracker  235  that uses a global inode list, according to certain embodiments. Global inode list  215  (which is a parent directory list for directories  265 ( 1 )-(N)) includes a directory inode field  255  and a sequential flag field  260 . Global inode list  215  is created and maintained in memory, and includes directory inodes  130 ( 1 )-(N) and sequential flags  220 ( 1 )-(N). Sequential flags can be stored as part of in-core inodes for parent directories. Directory access tracker  235  includes a sequential directory access tracker  270  and a non-sequential directory access tracker  275 . 
     In one embodiment, an application accesses an inode (e.g., on-disk inode  165 ( 4 )). Directory access tracker  235  determines the parent directory of the inode (e.g., directory  265 ( 1 )), and whether an entry for the directory exists in global inode list  215 . If the entry for the directory exists in global inode list  215 , directory access tracker  235  determines whether a file structure of the directory is sequential or non-sequential (e.g., by determining whether the on-disk inodes in that directory are listed, and thus being accessed, in a sequential or non-sequential manner). If the entry for the directory does not exist in global inode list  215 , directory access tracker  235  adds a new entry for the parent directory inode in global inode list  215 . It should be noted that as shown in  FIGS. 1A, 2A, 2C and 3C , directory inodes (e.g., directory inodes  130 ( 1 )-(N)) are simply directory-specific representations of on-disk inodes that represent parent directories (e.g., instead of individual files). For example, directory inode  130 ( 1 ) is an in-memory data structure that represents a parent directory of one or more on-disk inodes. 
     To track sequential directory access of on-disk inodes, sequential directory access tracker  270  first finds a parent directory of a given on-disk inode (e.g., finds the parent directory&#39;s inode number). For example, if on-disk inode  165 ( 4 ) is read from disk  150 , sequential directory access tracker  270  finds a parent directory of on-disk inode  165 ( 4 ) (e.g., directory inode  130 ( 1 )). Sequential directory access tracker  270  then searches global inode list  215  for an entry of the parent directory (inode) of a given on-disk inode (e.g., whether the parent directory inode number is present in cache  205 ). 
     If the entry of the parent directory (inode) exists in global inode list  215 , sequential directory access tracker  270  checks global inode list  215  to determine whether the parent directory has a sequential flag set (e.g., directory inode  130 ( 1 ), which in this case, is the parent directory inode number, and has the sequential flag set as shown in  FIG. 2C ). If the sequential flag is set, metadata read-ahead generator  240  issues a metadata read-ahead instruction (e.g., to fetch all remaining on-disk inodes in directory  265 ( 1 ) because the on-disk inode access is sequential). If sequential directory access tracker  270  does not find the entry of the parent directory in global inode list  215 , sequential directory access tracker  270  adds a new entry of the parent directory&#39;s inode number to global inode list  215 . 
     To track non-sequential directory access of on-disk inodes, non-sequential directory access tracker  275  first finds a parent directory of a given on-disk inode (e.g., the parent directory&#39;s inode number). Non-sequential directory access tracker  275  then searches global inode list  215  for an existing entry of the parent directory (e.g., whether the parent directory inode number is present in cache  205 ). If the entry of the parent directory exists in global inode list  215 , non-sequential directory access tracker  275  fetches (or retrieves) an inode list of the parent directory (e.g., a portion or a part of inode list  175  applicable to the parent directory in question) from disk  150  into cache  205 , and metadata read-ahead generator  240  issues a metadata read-ahead instruction for the on-disk inodes listed on the retrieved inode list (e.g., on-disk inodes that are associated with and part of the parent directory). If the entry of the parent directory does not exist in global inode list  215 , non-sequential directory access tracker  275  adds a new entry of the parent directory&#39;s inode number to global inode list  215 . 
     Example of Issuing Metadata Read-Ahead Instructions for Modes 
       FIG. 2E  is a block diagram  200 E of a metadata read-ahead generator, according to one embodiment. Metadata read-ahead generator  240  is implemented by computing device  105  and stores an issued metadata read-ahead value  280  and an asynchronous metadata read-ahead instruction  285 , and includes queue generator  290 . Although directory access tracker  235  identifies one or more on-disk inodes to pre-fetch, if these on-disk inodes are not pre-fetched, I/O operations associated with these on-disk inodes cannot be completed. 
     Therefore, in one embodiment, metadata read-ahead generator  240  intercepts a command to read on-disk inodes in response to an I/O operation (e.g., a read operation or a write operation). An I/O operation to access data can result in (or cause) a command to access and read on-disk inode(s) (e.g., metadata) associated with that data (e.g., to determine when and how the requested data has been modified, and the like). Metadata read-ahead generator  240  analyzes issued metadata read-ahead value  280  in the metadata read-ahead operation by comparing issued metadata read-ahead value  280  and a chunk total in the command. 
     Issued metadata read-ahead value  280  includes all the on-disk inodes that should be read ahead (e.g., detected based on sequential/near-sequential chunk access, and/or sequential or non-sequential access of on-disk inodes in directories). A chunk total is the total number of chunks of on-disk inodes to be read ahead (e.g., represented as an integer “N” herein for discussion purposes). For example, chunk access tracker  230  and sequential directory access tracker  270  can identify and determine that a 1 KB chunk of on-disk inodes (e.g., on-disk inodes  165 ( 1 )-( 4 )) or a 2 k chunk of on-disk inodes (e.g., on-disk inodes  165 ( 1 )-( 8 )) must be read-ahead (e.g., based on sequential/near-sequential chunk access, and/or sequential or non-sequential access of on-disk inodes in directories). However, as discussed above, non-sequential directory access tracker  275  can identify several non-sequential on-disk inodes (e.g., that can be part of various disparate chunks) to read ahead (e.g., as shown in the case of directory  265 ( 2 ) in  FIG. 3B ). Therefore, it will be appreciated that in certain scenarios, issued metadata read-ahead value  280  may or may not be equal to N. 
     In some embodiments, based on comparing issued metadata read-ahead value  280  and the chunk total in the command, metadata read-ahead generator  240  either waits for the I/O operation to complete, or issues asynchronous metadata read-ahead instruction  285 . If the I/O operation is complete, queue generator  290  generates a queue and includes the remaining chunks of metadata of the chunk total not included in asynchronous metadata read-ahead instruction  285 . However, if the I/O operation is incomplete, queue generator  290  updates the chunk total in the metadata read-ahead operation. 
     For example, a command (or call) to read an on-disk inode which goes to disk  150  is intercepted after an I/O operation is issued (e.g., by application  130 ). This command triggers the inode access pattern detection methods described above (e.g., sequential/near-sequential chunk access, and/or sequential or non-sequential access of on-disk inodes in directories). If the inode access pattern detection methods do not trigger a read-ahead of on-disk inodes, metadata read-ahead generator  240  simply waits for the I/O operation to complete. However, if the inode access pattern detection methods do trigger a read-ahead of on-disk inodes, metadata read-ahead generator  240  determines whether the total issued metadata read ahead (e.g., issued metadata read-ahead value  280 ) is less than or equal to N (e.g., the total number of chunks of on-disk inodes to be read ahead). 
     If the total issued metadata read ahead is less than or equal to N, metadata read-ahead generator  240  issues asynchronous metadata read-ahead instruction  285  with the next chunk of the asynchronous metadata read (e.g., the next chunk in issued metadata read-ahead value  280  after N). If the original I/O operation is complete, queue generator  290  generates a separate thread which issues asynchronous metadata read-ahead instruction  285  with the remaining chunks of the asynchronous metadata read (e.g., the remaining chunks in issued metadata read-ahead value  280  after N). If the original I/O operation is not complete, metadata read-ahead generator  240  increments a counter for issued metadata read-ahead value  280 , determines whether issued metadata read-ahead value  280  is equal to N, and waits for the original I/O operation to complete. 
     It will be appreciated that metadata read-ahead detection and the issuing of asynchronous metadata read-ahead instructions is performed in the context of the blocking thread, while the original I/O operation is waiting to complete in the background. These methodologies decrease inode access pattern detection overhead on system performance, and also avoid the creation and scheduling of separate threads, which can delay the availability of blocks for subsequent reads. 
     Example of Tracking Sequential and Non-Sequential Directory Access Pattern of Modes 
       FIG. 3A  is a block diagram of a directory with a sequential inode structure  300 A,  FIG. 3B  is a block diagram of a directory with a non-sequential inode structure  300 B, and  FIG. 3C  is a block diagram of a cache  300 C that implements a global inode list (e.g., a parent directory list or a global in-memory inode list), according to some embodiments. It will be appreciated that a listing of directories is first performed by an application (e.g., by application  135 , application  140 , or some other application). During the listing of directories, on-disk inode numbers associated with each directory entry are returned. If the on-disk inode numbers within a given directory are sequential (e.g., directory  265 ( 1 ) as shown in  FIG. 3A ), then sequential directory access tracker  270  sets a sequential flag for that particular directory in the in-core inode of that directory (e.g., a sequential flag for directory  265 ( 1 ) is set in global inode list  215  as shown in  FIGS. 2C and 3C ). 
     For example, because the on-disk inodes of directory  265 ( 1 ) are sequential (e.g., on-disk inodes  165 ( 4 )-( 9 ) are listed sequentially), sequential directory access tracker  270  sets a sequential flag in directory inode  130 ( 1 ) (e.g., in an in-core inode) for directory  265 ( 1 ) (e.g., indicated by “1” in sequential flag field  260  of global inode list  215  in  FIGS. 2C and 3C ). On the contrary, because the on-disk inodes of directory  265 ( 2 ) are non-sequential (e.g., on-disk inodes  165 ( 4 ),  165 ( 9 ),  165 ( 15 ),  165 ( 11 ),  165 ( 19 ), and  165 ( 6 ) are listed non-sequentially), non-sequential directory access tracker  275  does not set a sequential flag in directory inode  130 ( 2 ) (e.g., in an in-core inode) for directory  265 ( 2 )) (e.g., indicated by “0” in sequential flag field  260  of global inode list  215  in  FIGS. 2C and 3C ). 
     As previously noted, a metadata read-ahead instruction to perform a metadata read-ahead operation can be issued after a listing of a directory is performed. In one embodiment, an application performs the listing of directories that are part of disk  150 . For example, a listing of directory  265 ( 2 ) as shown in  FIG. 3B , returns file  315 ( 1 ) with on-disk inode  165 ( 4 ), file  315 ( 2 ) with on-disk inode  165 ( 9 ), file  315 ( 3 ) with on-disk inode  165 ( 15 ), file  315 ( 4 ) with on-disk inode  165 ( 11 ), file  315 ( 5 ) with on-disk inode  165 ( 19 ), and file  315 ( 6 ) with on-disk inode  165 ( 6 ). In this scenario, directory access tracker  235  creates and maintains an in-memory data structure (e.g., an in-memory inode list) that includes a list of the foregoing inode numbers (e.g., on-disk inodes  165 ( 4 ),  165 ( 9 ),  165 ( 15 ),  165 ( 11 ),  165 ( 19 ), and  165 ( 6 )), and associates this in-memory inode list with the in-core inode of directory  265 ( 2 ) (e.g., directory inode  130 ( 2 )). 
     For example, if application  130  accesses file  315 ( 1 ), and hence there is a need to access and read on-disk inode  165 ( 4 ), non-sequential directory access tracker  275  reads on-disk inode  165 ( 4 ) from disk  150 , and determines that the parent directory inode number of on-disk inode  165 ( 4 ) is directory inode  130 ( 2 ). Non-sequential directory access tracker  275  then checks if directory inode  130 ( 2 ) is present in cache  205 , as shown in  FIG. 3C . If directory inode  130 ( 2 ) is not present in cache  205 , non-sequential directory access tracker  275  adds directory inode  130 ( 2 ) (e.g., indicated by bold in  FIGS. 2C and 3C ) to cache  205 . 
     Next, if application  130  accesses file  315 ( 2 ), and thus accesses and reads on-disk inode  165 ( 9 ) from disk  150 , non-sequential directory access tracker  275  determines that the parent directory inode number of on-disk inode  165 ( 9 ) is also directory inode  130 ( 2 ). Because directory inode  130 ( 2 ) has been added to cache  205 , metadata read-ahead generator  240  determines that the remaining files (e.g., files  315 ( 3 )-( 6 )) under directory  265 ( 2 ) can be read ahead. Metadata read-ahead generator  240  then accesses the in-memory inode list and identifies the remaining on-disk inode numbers associated with files  315 ( 3 )-( 6 ) (e.g., on-disk inodes  165 ( 15 ),  165 ( 11 ),  165 ( 19 ), and  165 ( 6 )), and generates a metadata read-ahead instruction that performs a metadata read-ahead operation to fetch on-disk inodes  165 ( 15 ),  165 ( 11 ),  165 ( 19 ), and  165 ( 6 ) from disk  150  to memory  115 . 
     It will be appreciated that directory access tracker  235  tracks chunk access pattern(s) of on-disk inodes, as well as sequential and non-sequential access pattern(s) of on-disk inodes that are part of directories, to identify on-disk inodes that are candidates for a metadata read-ahead operation that accelerates inode and data access. 
     Processes to Track Inode Access Pattern(s) and Issue Metadata Read-Ahead Instructions 
       FIG. 4A  is a flowchart  400 A that illustrates a process for issuing a read-ahead instruction to pre-fetch on-disk inodes from disk to memory, according to one embodiment. The process begins at  405  by accessing a metadata storage area (e.g., structural file  160 ). At  410 , the process determines the location of a last read chunk of metadata (e.g., end offset of last read metadata chunk  245 ). At  415 , the process determines if a command (or call) (e.g., to read on-disk inodes) has been received. If no command has been received yet, the process loops back to  415 . However, if a command has been received, the process, at  420 , determines the location of an object of the command in the metadata storage area (e.g., starting offset of current metadata read operation  250 ). 
     At  425 , the process determines whether a metadata read-ahead can be performed (or whether a metadata read-ahead is required or feasible). If a metadata read-ahead cannot be performed, the process, at  430 , permits normal processing (e.g., no metadata read-ahead operation is performed and on-disk inodes are not pre-fetched from disk into memory). However, if a metadata read-ahead can be performed (and/or is needed and/or feasible), the process, at  435 , issues a metadata read-ahead operation (or issues a metadata read-ahead instruction, e.g., using metadata read-ahead generator  240 , that causes computing device  105  to perform a metadata read-ahead operation to fetch chunk(s) of on-disk inodes from disk into memory). At  440 , the process determines if there is a new command (e.g., to access and/or read on-disk inodes). If there is a new command to access and/or read on-disk inodes, the process loops back to  405 . Otherwise, the process ends. 
       FIG. 4B  is a flowchart  400 B that illustrates a process for storing offset metadata associated with on-disk inodes, according to one embodiment. The process begins at  445  by determining an offset location of a chunk of metadata (e.g., end offset of last read metadata chunk  245 ) in a metadata storage area (e.g., structural file  160 ). At  450 , the process creates an in-core inode (e.g., in-core inode list  125 ) in memory (e.g., memory  115 ), and at  455 , the process stores the offset location of the chunk of metadata in the in-core inode. 
     At  455 , the process determines whether a location of a current metadata read operation (e.g., starting offset of current metadata read operation  250 ) is next to (or adjacent to) the offset location of the chunk of metadata. If the location of the current metadata read operation is not next to the offset location of the chunk of metadata, the process, at  465 , stores an offset location of a chunk of metadata read by the current metadata read operation (e.g., an end offset of the current metadata read operation). However, if the location of the current metadata read operation is next to the offset location of the chunk of metadata, the process, at  470 , issues a metadata read-ahead operation (or issues a metadata read-ahead instruction), and at  475 , stores an offset location of a chunk of metadata read by the metadata read-ahead operation. At  480 , the process determines whether there is a new read call (e.g., a command to read on-disk inodes caused by an application I/O operation). If there is a new read call to read on-disk inodes, the process loops back to  460 . Otherwise, the process ends. 
     It will be appreciated that the processes illustrated in flowchart  400 A of  FIG. 4A  and flowchart  400 B of  FIG. 4B  are examples of tracking the chunk access patterns of on-disk inodes. Because on-disk inodes are persistently stored on disk (e.g., disk  150 ), chunk access tracker  230  can access structural file  160  to determine the end offset of a last read metadata chunk as well as the starting offset of a current metadata read operation. Because chunk access tracker  230  can save this location information, chunk access tracker  230  can determine whether on-disk inodes are being accessed by application  135  or application  140  in a sequential or nearly-sequential manner. Based on this stored location information, on-disk inodes that are likely to be accessed can be read ahead and pre-fetched from disk into memory, thus accelerating subsequent inode access for those on-disk inodes. 
       FIG. 5A  is a flowchart  500 A that illustrates a process for determining the file structure of a directory, according to one embodiment. The process begins at  505  by accessing a file within a directory (e.g., file  135 ( 1 ) in directory  265 ( 1 ) as shown in  FIG. 3A  or file  135 ( 1 ) in directory  265 ( 2 ) as shown in  FIG. 3B ). At  510 , the process searches a global inode list for an entry (e.g., an inode number) of the directory. At  515 , the process determines whether the directory exists in the global inode list (e.g., whether directory inode  130 ( 1 ), which is the inode number of directory  265 ( 1 ), exists and is listed in global inode list  215 ). 
     If the directory does not exist in the global inode list, the process, at  520 , adds a new entry (e.g., adds a parent directory inode number) for an on-disk inode in the global inode list (e.g., shown with respect to directory  265 ( 3 ) in  FIGS. 2C and 3C ). If the directory exists in the global inode list, the process, at  525 , determines a file structure of the directory (e.g., whether the on-disk inodes in the directory are listed sequentially or non-sequentially). At  530 , the process determines whether there is another access of on-disk inodes. If there is another access of on-disk inodes, the process loops back to  505 . Otherwise, the process ends. 
       FIG. 5B  is a flowchart  500 B that illustrates a process for issuing a metadata read-ahead instruction for on-disk inodes, according to one embodiment. The process begins at  535  by determining whether on-disk inode numbers of entries within a given directory are sequential or non-sequential (e.g., listed sequentially or non-sequentially as the result of performing a listing of the directory). For example, in  FIG. 3A , the on-disk inode numbers of entries are listed sequentially, and in  FIG. 3B , the on-disk inode numbers of entries are listed non-sequentially. 
     If the on-disk inode numbers of entries are listed non-sequentially, the process, at  540 , access a global inode list (e.g., a parent directory list as shown in  FIG. 3C ). At  545 , the process identifies the parent directory inode on the global inode list (e.g., using the on-disk inode&#39;s parent directory inode number). At  550 , the process fetches an inode list associated with the directory in question (e.g., from disk  150 , or from memory because the inode list can be stored and maintained in memory during the listing process), and at  555 , the issues a metadata read-ahead instruction for on-disk inodes on the inode list. 
     However, if the on-disk inode numbers of entries are listed sequentially, the process, at  560 , access the global inode list, and at  565 , identifies an in-memory inode of the parent directory of a file that is accessed on the global inode list (e.g., using the on-disk inode&#39;s parent directory inode number). At  570 , the process verifies that the directory has the sequential flag set, and at  575 , issues a metadata read-ahead instruction for the remaining on-disk inodes listed in the directory in question. At  580 , the process determines whether there is another access of on-disk inode(s). If there is another access of on-disk inode(s), the process loops back to  535 . Otherwise, the process ends. 
     It will be appreciated that the processes illustrated in flowchart  500 A of  FIG. 5A  and flowchart  500 B of  FIG. 5B  are examples of using a parent directory list to track access pattern(s) of on-disk inodes when directories are involved. As previously noted, an application can perform a listing of one or more directories to determine whether on-disk inodes in a given directory are listed sequentially or non-sequentially. Because directories are typically stored on disk (e.g., disk  150 ), determining a directory&#39;s data and/or file structure each time a file is accessed in a given directory can consume significant computing resources. However, because both access pattern tracker  225  and the parent directory list are part of memory  115 , and because the parent directory list maintains a listing of the data and/or file structure of multiple directories, access pattern tracker  225  can simply use the parent directory list to determine whether a given directory&#39;s in-core inodes are sequential or non-sequential, without accessing disk  150  each time a file in a given directory is accessed. 
       FIG. 6A  is a flowchart  600 A that illustrates a process for processing input/output (I/O) operations related to pre-fetching inodes, according to one embodiment. The process begins at  605  by detecting an I/O operation issued for a chunk of metadata associated with an on-disk inode (e.g., a unit of metadata in structural file  160 ). At  610 , the process determines whether the I/O operation is detected. If the I/O operation is not detected, the process loops back to  605 . However, if the I/O operation is detected, the process, at  615 , intercepts a command (or call) to access and/or read on-disk inode(s). 
     At  620 , the process accesses a metadata read-ahead value of the metadata read-ahead operation, and at  625 , analyzes the metadata read-ahead value by comparing the (total issued) metadata read-ahead value to the total number of chunks of metadata to be read ahead. At  630 , the process waits for the I/O operation to complete, and at  635 , issues an asynchronous metadata read-ahead instruction (e.g., using metadata read-ahead generator  240 ). At  640 , the process determines if there is another I/O operation. If there is another I/O operation, the process loops to  605 . Otherwise, the process ends. 
       FIG. 6B  is a flowchart that illustrates a process for processing I/O operations related to pre-fetching inodes, according to one embodiment. The process begins at  645  by determining whether a given I/O operation is complete. If the I/O operation is not complete, the process, at  650 , updates a chunk total (e.g., a total number of chunks of metadata to be read-ahead or “N”), and proceeds to  625  (in  FIG. 6A ). However, if the I/O operation is complete, the process, at  660 , generates a queue (e.g., a separate thread), and at  665 , issues a metadata read-ahead that includes the remaining chunks of metadata not included in the asynchronous metadata read-ahead instruction (e.g., of  FIG. 6A ). At  670 , the process determines if there is another command (e.g., a call to read on-disk inode(s)) to be intercepted. If there is another command to be intercepted, the process loops back to  615  (in  FIG. 6A ). Otherwise, the process ends. 
     It will be appreciated that the processes illustrated in flowchart  600 A of  FIG. 6A  and flowchart  600 B of  FIG. 6B  can be used to identify and pre-fetch on-disk inodes that are part of various disparate chunks of metadata by comparing an issued metadata read-ahead value and a chunk total. Because all or a portion of an inode list can be pre-fetched into memory during a directory listing process, on-disk inodes that are candidates for a metadata read-ahead instruction can be identified in cases where such on-disk are not accessed sequentially. Further, it will also be appreciated that the metadata read-ahead detection and the issuing of asynchronous metadata read-ahead instructions is performed in the context of the blocking thread, while the original I/O operation is waiting to complete in the background. These methodologies decrease inode access pattern detection overhead on system performance, and also avoid the creation and scheduling of separate threads, which can delay the availability of blocks for subsequent reads. 
       FIG. 7A  is a flowchart that illustrates a process for processing access of on-disk inodes and adding an entry of a directory to a global inode list, according to certain embodiments. The process begins at  705  by determining whether there is an access of on-disk inode(s) (e.g., a read command/call of on-disk inode(s) caused by one or more I/O operations). If there is no access of on-disk inode(s), the process loops back to  705 . However, if there is access of on-disk inode(s), the process, at  710 , identifies a directory associated with the on-disk inode(s) (e.g., using a parent directory inode number). At  715 , the process access a global inode list (e.g., global inode list  215  and/or a parent directory list). 
     At  720 , the process determines whether the directory is on the global inode list (e.g., whether the parent directory inode number of the inode exists on the global inode list). If the directory is not on the global inode list, the process, at  725 , adds the directory to the global inode list (e.g., by adding an entry for the parent directory inode number of the inode to the global inode list). However, if the directory is on the global inode list, the process, at  730 , verifies that a sequential flag is set for the directory, and at  735 , issues a metadata read-ahead instruction (e.g., for the remaining on-disk inodes that are listed in (or part of) the directory). At  740 , the process determines whether there is another access (e.g., of on-disk inode(s)). If there is another access, the process loops back to  705 . Otherwise, the process ends. 
       FIG. 7B  is a flowchart that illustrates a process for processing a request to access on-disk inodes, according to one embodiment. The process begins at  745  by detecting an I/O operation. At  750 , the process intercepts a command (or call) to access (or read) on-disk inode(s). At  755 , the process determines whether an on-disk inode access pattern (e.g., detected based on chunk access, and sequential or non-sequential access, among other methodologies) triggers, causes, or results in a metadata read-ahead of the on-disk inode(s). If the on-disk inode access pattern does not trigger the metadata read-ahead (e.g., based on chunk access, sequential access, or non-sequential access), the process, at  760 , waits for the I/O operation to complete. It should be noted that an example process for waiting for the I/O operation to complete is illustrated in flowchart  600 B of  FIG. 6B . 
     However, if the on-disk inode access pattern does trigger the metadata read-ahead, the process, at  765 , determines whether a chunk total (e.g., a total number of chunks of on-disk inode metadata to be read ahead or “N”) is less than or equal to a metadata read-ahead value (e.g., issued metadata read-ahead value  280  or a total issued metadata read-ahead value). If the chunk total is not less than or equal to the metadata read-ahead value, the process, at  760 , waits for the I/O operation to complete. However, if the chunk total is less than or equal to the metadata read-ahead value, the process, at  770 , issues a next chunk of asynchronous metadata read-ahead, and at  775 , determines whether the I/O operation is complete. If the I/O operation is not complete, the process, at  780 , increments a counter (e.g., for the issued metadata read-ahead), and loops back to  765 . However, if the I/O operation is complete, the process, at  785 , generates a separate thread and issues the remaining chunks of the asynchronous metadata read-ahead. At  790 , the process determines if there is another I/O operation. If there is another I/O operation, the process loops back to  745 . Otherwise, the process ends. 
     Typically, if an I/O operation is blocked, a thread cannot progress any further. It will be appreciated that because the methods, systems, and processes of inode access pattern detection and metadata read-ahead generation are performed in the context of the blocking thread (and while the original I/O is waiting for completion in the background), inode access pattern detection overhead on system performance is reduced. In addition, permitting the original I/O operation to complete can also avoid the cost of creating and scheduling separate threads (which can delay the availability of data blocks for subsequent read operations). 
     Further, it should be noted that other data structures such as attributes can be associated with nodes. The methods, systems, and processes related to inode access pattern detection and issuing metadata read-ahead instructions described herein can pre-populate these (other) data structures in memory and can initialize various inode locks asynchronously. Therefore, it will be appreciated that the methods, systems, and processes described herein are capable of tracking access patterns of inodes based on chunk access, sequential access, and non-sequential access, and issuing read-ahead instructions for inodes, among other capabilities. 
     Example Computing Environment 
       FIG. 8  is a block diagram of a computing system  800 , illustrating how an access pattern tracker and a metadata read-ahead generator can be implemented in software, according to one embodiment. Computing system  800  broadly represents any single or multi-processor computing device or system capable of executing computer-readable instructions. Examples of computing system  800  include, without limitation, any one or more of a variety of devices including workstations, personal computers, laptops, client-side terminals, servers, distributed computing systems, handheld devices (e.g., personal digital assistants and mobile phones), network appliances, storage controllers (e.g., array controllers, tape drive controller, or hard drive controller), and the like. In its most basic configuration, computing system  800  may include at least one processor  110  and a memory  115 . By executing the software that implements computing device  105 , computing system  800  becomes a special purpose computing device that is configured to track inode access pattern(s) and issue read-ahead instructions for inodes. 
     Processor  110  generally represents any type or form of processing unit capable of processing data or interpreting and executing instructions. In certain embodiments, processor  110  may receive instructions from a software application or module. These instructions may cause processor  110  to perform the functions of one or more of the embodiments described and/or illustrated herein. For example, processor  110  may perform and/or be a means for performing all or some of the operations described herein. Processor  110  may also perform and/or be a means for performing any other operations, methods, or processes described and/or illustrated herein. 
     Memory  115  generally represents any type or form of volatile or non-volatile storage devices or mediums capable of storing data and/or other computer-readable instructions. Examples include, without limitation, random access memory (RAM), read only memory (ROM), flash memory, or any other suitable memory device. Although not required, in certain embodiments computing system  800  may include both a volatile memory unit and a non-volatile storage device. In one example, program instructions implementing an access pattern tracker and a metadata read-ahead generator may be loaded into memory  115 . 
     In certain embodiments, computing system  800  may also include one or more components or elements in addition to processor  110  and/or memory  115 . For example, as illustrated in  FIG. 8 , computing system  800  may include a memory controller  820 , an Input/Output (I/O) controller  835 , and a communication interface  845 , each of which may be interconnected via a communication infrastructure  805 . Communication infrastructure  805  generally represents any type or form of infrastructure capable of facilitating communication between one or more components of a computing device. Examples of communication infrastructure  805  include, without limitation, a communication bus (such as an Industry Standard Architecture (ISA), Peripheral Component Interconnect (PCI), PCI express (PCIe), or similar bus) and a network. 
     Memory controller  820  generally represents any type/form of device capable of handling memory or data or controlling communication between one or more components of computing system  800 . In certain embodiments memory controller  820  may control communication between processor  110 , memory  115 , and I/O controller  835  via communication infrastructure  805 . In certain embodiments, memory controller  820  may perform and/or be a means for performing, either alone or in combination with other elements, one or more of the operations or features described and/or illustrated herein. 
     I/O controller  835  generally represents any type or form of module capable of coordinating and/or controlling the input and output functions of one or more computing devices such as computing device  105 . For example, in certain embodiments I/O controller  835  may control or facilitate transfer of data between one or more elements of computing system  800 , such as processor  110 , memory  115 , communication interface  845 , display adapter  815 , input interface  825 , and/or storage interface  840 . 
     Communication interface  845  broadly represents any type or form of communication device or adapter capable of facilitating communication between computing system  800  and one or more other devices. Communication interface  845  may facilitate communication between computing system  800  and a private or public network including additional computing systems. Examples of communication interface  845  include, without limitation, a wired network interface (such as a network interface card), a wireless network interface (such as a wireless network interface card), a modem, and any other suitable interface. Communication interface  845  may provide a direct connection to a remote server via a direct link to a network, such as the Internet, and may also indirectly provide such a connection through, for example, a local area network (e.g., an Ethernet network), a personal area network, a telephone or cable network, a cellular telephone connection, a satellite data connection, or any other suitable connection. 
     Communication interface  845  may also represent a host adapter configured to facilitate communication between computing system  800  and one or more additional network or storage devices via an external bus or communications channel. Examples of host adapters include, Small Computer System Interface (SCSI) host adapters, Universal Serial Bus (USB) host adapters, Institute of Electrical and Electronics Engineers (IEEE) 1394 host adapters, Serial Advanced Technology Attachment (SATA), Serial Attached SCSI (SAS), and external SATA (eSATA) host adapters, Advanced Technology Attachment (ATA) and Parallel ATA (PATA) host adapters, Fibre Channel interface adapters, Ethernet adapters, or the like. Communication interface  845  may also allow computing system  800  to engage in distributed or remote computing (e.g., by receiving/sending instructions to/from a remote device for execution). 
     As illustrated in  FIG. 8 , computing system  800  may also include at least one display device  810  coupled to communication infrastructure  805  via a display adapter  815 . Display device  810  generally represents any type or form of device capable of visually displaying information forwarded by display adapter  815 . Similarly, display adapter  815  generally represents any type or form of device configured to forward graphics, text, and other data from communication infrastructure  805  (or from a frame buffer, as known in the art) for display on display device  810 . Computing system  800  may also include at least one input device  830  coupled to communication infrastructure  805  via an input interface  825 . Input device  830  generally represents any type or form of input device capable of providing input, either computer or human generated, to computing system  800 . Examples of input device  830  include a keyboard, a pointing device, a speech recognition device, or any other input device. 
     Computing system  800  may also include storage device  850  (e.g., disk  150 ) coupled to communication infrastructure  805  via a storage interface  840 . Storage device  850  generally represents any type or form of storage devices or mediums capable of storing data and/or other computer-readable instructions. For example, storage device  850  may include a magnetic disk drive (e.g., a so-called hard drive), a floppy disk drive, a magnetic tape drive, an optical disk drive, a flash drive, or the like. Storage interface  840  generally represents any type or form of interface or device for transferring and/or transmitting data between storage device  850 , and other components of computing system  800 . Storage device  850  may be configured to read from and/or write to a removable storage unit configured to store computer software, data, or other computer-readable information. Examples of suitable removable storage units include a floppy disk, a magnetic tape, an optical disk, a flash memory device, or the like. Storage device  850  may also include other similar structures or devices for allowing computer software, data, or other computer-readable instructions to be loaded into computing system  800 . For example, storage device  850  may be configured to read and write software, data, or other computer-readable information. Storage device  850  may also be a part of computing system  800  or may be separate devices accessed through other interface systems. 
     Many other devices or subsystems may be connected to computing system  800 . Conversely, all of the components and devices illustrated in  FIG. 8  need not be present to practice the embodiments described and/or illustrated herein. The devices and subsystems referenced above may also be interconnected in different ways from that shown in  FIG. 8 . Computing system  800  may also employ any number of software, firmware, and/or hardware configurations. For example, one or more of the embodiments disclosed herein may be encoded as a computer program (also referred to as computer software, software applications, computer-readable instructions, or computer control logic) on a computer-readable storage medium. Examples of computer-readable storage media include magnetic-storage media (e.g., hard disk drives and floppy disks), optical-storage media (e.g., CD- or DVD-ROMs), electronic-storage media (e.g., solid-state drives and flash media), and the like. Such computer programs can also be transferred to computing system  800  for storage in memory via a network such as the Internet or upon a carrier medium. 
     The computer-readable medium containing the computer program may be loaded into computing system  800 . All or a portion of the computer program stored on the computer-readable medium may then be stored in memory  860  and/or various portions of storage device  850 . When executed by processor  110 , a computer program loaded into computing system  800  may cause processor  110  to perform and/or be a means for performing the functions of one or more of the embodiments described and/or illustrated herein. Additionally or alternatively, one or more of the embodiments described and/or illustrated herein may be implemented in firmware and/or hardware. For example, computing system  800  may be configured as an application specific integrated circuit (ASIC) adapted to implement one or more of the embodiments disclosed herein. 
     Example Networking Environment 
       FIG. 9  is a block diagram of a networked system  900 , illustrating how various devices can communicate via a network, according to one embodiment. In certain embodiments, network-attached storage (NAS) devices may be configured to communicate with computing device  105  and storage system  145  using various protocols, such as Network File System (NFS), Server Message Block (SMB), or Common Internet File System (CIFS), among others. 
     Network  185  generally represents any type or form of computer network or architecture capable of facilitating communication between computing device  105  and storage system  145 . In certain embodiments, a communication interface, such as communication interface  845  in  FIG. 8 , may be used to provide connectivity between computing device  105 , storage system  145 , and network  155 . It should be noted that the embodiments described and/or illustrated herein are not limited to the Internet or any particular network-based environment. For example, network  185  can be a Storage Area Network (SAN). Computing device  105  and storage system  145  can be integrated or separate. If separate, for example, computing device  105  and storage system  145  can be coupled by a local connection (e.g., using Bluetooth™, Peripheral Component Interconnect (PCI), Small Computer System Interface (SCSI), or the like), or via one or more networks such as the Internet, a LAN, or a SAN. 
     In one embodiment, all or a portion of one or more of the disclosed embodiments may be encoded as a computer program and loaded onto and executed by computing device  105 , inode access pattern tracking and metadata read-ahead instruction issuing system  910 , inode access pattern tracking system  940 , and/or metadata read-ahead instruction generation system  950 . All or a portion of one or more of the embodiments disclosed herein may also be encoded as a computer program, stored on computing device  105 , inode access pattern tracking and metadata read-ahead instruction issuing system  910 , and/or inode access pattern tracking system  940 , and distributed over network  185 . 
     In some examples, all or a portion of computing device  105  may represent portions of a cloud-computing or network-based environment. Cloud-computing environments may provide various services and applications via the Internet. These cloud-based services (e.g., software as a service, platform as a service, infrastructure as a service, etc.) may be accessible through a web browser or other remote interface. Various functions described herein may be provided through a remote desktop environment or any other cloud-based computing environment. 
     In addition, one or more of the components described herein may transform data, physical devices, and/or representations of physical devices from one form to another. For example, computing device  105  and/or inode access pattern tracking and metadata read-ahead instruction issuing system  910  may transform the behavior of computing device  105  in order to cause computing device  105  and/or inode access pattern tracking and metadata read-ahead instruction issuing system  910  to track access pattern(s) of inodes and issue read-ahead instructions. 
     Although the present disclosure has been described in connection with several embodiments, the disclosure is not intended to be limited to the specific forms set forth herein. On the contrary, it is intended to cover such alternatives, modifications, and equivalents as can be reasonably included within the scope of the disclosure as defined by the appended claims.