System and method for using a memory buffer to stream data from a tape to multiple clients

Abstract

Embodiments described herein provide systems and methods for streaming data to multiple reading clients. More particularly, embodiments described herein provide systems and methods for using a memory buffer to stream file data from a mounted tape file system volume to multiple reading clients.

What is claimed is: 
     
         1 . A system for providing a network based file system, comprising:
 a memory;   a processor;   a computer readable storage medium storing a set of computer program instructions, the set of computer program instructions comprising instructions executable to:
 for a request for a file partially stored in a disk-based cache, 
 initiate a tape streaming session corresponding to the file; 
 allocate a buffer in the memory for the tape streaming session, wherein the buffer is a circular buffer; 
 during the tape streaming session:
 store file data in the buffer read from an LTFS volume; 
 restore the file to the disk-based cache from the buffer; 
 reply to read requests for file data of the file from non-lagging network file system interface clients associated with the tape streaming session from the buffer; and 
 reply to read requests for file data of the file from lagging network file system interface clients from the disk-based cache. 
 
   
     
     
         2 . The system of  claim 1 , wherein the tape streaming session comprises:
 a tape data producer configured to write file data into the buffer;   one or more consumers configured to read data from the buffer; and   wherein the set of computer program instructions further comprise instructions executable to expel lagging consumers from the tape streaming session.   
     
     
         3 . The system of  claim 2 , wherein the set of computer program instructions are further comprise instructions executable to determine that a consumer is lagging if a data available size for that consumer equals a buffer size of the circular buffer. 
     
     
         4 . The system of  claim 2 , wherein the set of computer program instructions further comprise instructions executable to:
 maintain an absolute producer index and virtual producer index;   maintain an absolute consumer index for each of the one or more consumers and a virtual consumer index for each of the one or more consumers; and   for a consumer, delete the absolute consumer index and virtual consumer index for that consumer if that consumer is expelled from the tape streaming session.   
     
     
         5 . The system of  claim 4 , wherein the set of computer program instructions further comprise instructions executable to map linear file positions to positions in the buffer. 
     
     
         6 . The system of  claim 2 , wherein the one or more consumers comprise a file restoration consumer and one or more client consumers. 
     
     
         7 . The system of  claim 6 , wherein the set of computer program instructions further comprise instructions executable to add a client consumer to the tape streaming session for each network file system interface client from which an “open” command is received for the file within a defined portion of the tape streaming session. 
     
     
         8 . A computer program product comprising a non-transitory computer readable medium storing a set of computer program instructions comprising instructions executable to:
 for a request for a file partially stored in a disk-based cache, initiate a tape streaming session corresponding to the file;   allocate a buffer in memory for the tape streaming session, wherein the buffer is a circular buffer;   during the tape streaming session:
 store file data in the buffer read from an LTFS volume; 
 restore the file to the disk-based cache from the buffer; 
 reply to read requests for file data of the file from non-lagging network file system interface clients associated with the tape streaming session from the buffer; and 
 reply to read requests for file data of the file from lagging network file system interface clients from the disk-based cache. 
   
     
     
         9 . The computer program product of  claim 8 , wherein the tape streaming session comprises:
 a tape data producer configured to write file data into the buffer;   one or more consumers configured to read data from the buffer:   wherein the set of computer program instructions further comprise instructions executable to expel lagging consumers from the tape streaming session.   
     
     
         10 . The computer program product of  claim 9 , wherein the set of computer program instructions are further comprise instructions executable to determine that a consumer is lagging if a data available size for that consumer equals a buffer size of the circular buffer. 
     
     
         11 . The computer program product of  claim 9 , wherein the set of computer program instructions further comprise instructions executable to:
 maintain an absolute producer index and virtual producer index;   maintain an absolute consumer index for each of the one or more consumers and a virtual consumer index for each of the one or more consumers; and   for a consumer, delete the absolute consumer index and virtual consumer index for that consumer if that consumer is expelled from the tape streaming session.   
     
     
         12 . The computer program product of  claim 8 , wherein the set of computer program instructions further comprise instructions executable to map linear file positions to positions in the buffer. 
     
     
         13 . The computer program product of  claim 9 , wherein the one or more consumers comprise a file restoration consumer and one or more client consumers. 
     
     
         14 . The computer program product of  claim 13 , wherein the set of computer program instructions further comprise instructions executable to add a client consumer to the tape streaming session for each network file system interface client from which an “open” command is received for the file within a defined portion of the tape streaming session. 
     
     
         15 . A method for streaming file data from a tape file comprising:
 interfacing with a media library having tapes storing files according to a tape file system;   maintaining a read cache of files in a data store, the read cache containing file stubs of files in the media library;   presenting a network file system interface to clients;   for a request for a file having a file stub in the read cache,
 initiating a tape streaming session corresponding to the file; 
 allocating a buffer in memory for the tape streaming session, wherein the buffer is a circular buffer; 
 during the tape streaming session:
 storing file data for the file in the buffer read from a tape file system volume; 
 restoring the file to the data store from the buffer; 
 replying to read requests for file data of the file from the buffer for read requests from non-lagging network file system interface clients associated with the tape streaming session; and 
 replying to read requests for file data of the file from the data store from lagging network file system interface clients. 
 
   
     
     
         16 . The method of  claim 15 , wherein:
 the tape streaming session comprises:
 a tape data producer configured to write file data into the buffer; 
 one or more consumers configured to read data from the buffer; and 
   the method further comprises expelling lagging consumers from the tape streaming session.   
     
     
         17 . The method of  claim 16 , further comprising determining that a consumer is lagging if a data available size for that consumer equals a buffer size of the circular buffer. 
     
     
         18 . The method of  claim 16 , further comprising:
 maintaining an absolute producer index and virtual producer index;   maintaining an absolute consumer index for each of the one or more consumers and a virtual consumer index for each of the one or more consumers; and   for a consumer, deleting the absolute consumer index and virtual consumer index for that consumer if that consumer is expelled from the tape streaming session.   
     
     
         19 . The method of  claim 18 , further comprising mapping linear file positions to positions in the buffer. 
     
     
         20 . The method of  claim 16 , wherein the one or more consumers comprise a file restoration consumer and one or more client consumers. 
     
     
         21 . The method of  claim 20 , further comprising adding a client consumer to the tape streaming session for each network file system interface client from which an “open” command is received for the file within a defined portion of the tape streaming session.