Clustered filesystem with membership version support

Abstract

A computer system with read/write access to storage devices creates a snapshot of a data volume at a point in time while continuing to accept access requests to the mirrored data volume by copying before making changes to the base data volume. Multiple snapshots may be made of the same data volume at different points in time. Only data that is not stored in a previous snapshot volume or in the base data volume are stored in the most recent snapshot volume.

1 . (canceled) 
     
     
         2 . A method for maintaining a copy of a data volume, the method comprising:
 creating a first repository for storing file system data that is associated with a file system data volume stored in a persistent memory at a first time;   creating a first map that includes a first set of entries that are associated with the file system data volume stored in the persistent memory at the first time, wherein each respective entry of the first set of entries of the first map identify whether a particular region of a plurality of regions of the file system data volume has changed since the first time;   preventing the new write to the file system data volume from proceeding based on the identifying that the first region of the file system data volume is still in the initial state;   copying data from the first region of the file system data volume to the first data repository;   allowing the new write to the file system data volume to proceed after the data from the first region of the file system data volume has been copied to the first data repository; and   changing a state associated with a first entry in the first map from the initial state to a changed state after the new write to the file system data volume has completed.   
     
     
         3 . The method of  claim 2 , further comprising:
 receiving a read command from a requestor;   identifying that the read command addresses data that is associated with the first region;   identifying that data associated with the first region has changed since the first time;   reading the data associated with the read command and with the first region from the first data repository based on the identifying that the data associated with the first region has changed since the first time; and   providing the data associated with the read command and with the first region to the requestor.   
     
     
         4 . The method of  claim 3 , wherein the identifying that the data associated with the first region has changed since the first time is identified by accessing the first map and by identifying that the first entry is currently associated with the changed state. 
     
     
         5 . The method of  claim 2 , wherein each of the respective entries of the first set of entries each correspond to a particular number of bits of data of the file system data volume. 
     
     
         6 . The method of  claim 2 , further comprising:
 receiving a second read command;   identifying that the second read command addresses data that is associated with a second region of the file system data volume has not changed since the first time;   reading the data associated with the second read command from the file system data volume based on the identifying that the data associated with has not changed since the first time; and   providing the data associated with the second read command.   
     
     
         7 . The method of  claim 1 , wherein each of the plurality of regions of the file system data volume are associated with a first size, the first size corresponding to a number of bits of the first data repository. 
     
     
         8 . The method of  claim 7 , wherein each of the plurality of regions of the file system data volume are associated with a first size that corresponds to a number of bits identified by a user. 
     
     
         9 . The method of  claim 1 , wherein each of the respective entries of the first set of entries are set to an initial state, and the method further comprising:
 identifying that a new write to the file system data volume has been initiated to the first region of the plurality of regions of the file system data volume; and   identifying that a first map entry of the first map corresponds to the first region of the file system data volume is still in the initial state.   
     
     
         10 . A non-transitory computer readable storage medium having embodied thereon a program executable by a processor for performing a method for maintaining a copy of a data volume, the method comprising:
 creating a first repository for storing file system data that is associated with a file system data volume stored in a persistent memory at a first time;   creating a first map that includes a first set of entries that are associated with the file system data volume stored in the persistent memory at the first time, wherein each respective entry of the first set of entries of the first map identify whether a particular region of a plurality of regions of the file system data volume has changed since the first time,   preventing the new write to the file system data volume from proceeding based on the identifying that the first region of the file system data volume is still in the initial state;   copying data from the first region of the file system data volume to the first data repository;   allowing the new write to the file system data volume to proceed after the data from the first region of the file system data volume has been copied to the first data repository; and   changing a state associated with a first entry in the first map from the initial state to a changed state after the new write to the file system data volume has completed.   
     
     
         11 . The non-transitory computer readable storage of  claim 10 , the program further executable to:
 receive a read command from a requestor;   identify that the read command addresses data that is associated with the first region;   identify that data associated with the first region has changed since the first time;   read the data associated with the read command and with the first region from the first data repository based on the identifying that the data associated with the first region has changed since the first time; and   provide the data associated with the read command and with the first region to the requestor.   
     
     
         12 . The non-transitory computer readable storage of  claim 11 , wherein the identifying that the data associated with the first region has changed since the first time is identified by accessing the first map and by identifying that the first entry is currently associated with the changed state. 
     
     
         13 . The non-transitory computer readable storage medium of  claim 10 , wherein each of the respective entries of the first set of entries each correspond to a particular number of bits of data of the file system data volume. 
     
     
         14 . The non-transitory computer readable storage medium of  claim 10 , the program further executable to:
 receive a second read command;   identify that the second read command addresses data that is associated with a second region of the file system data volume has not changed since the first time;   read the data associated with the second read command from the file system data volume based on the identifying that the data associated with has not changed since the first time; and   provide the data associated with the second read command.   
     
     
         15 . The non-transitory computer readable storage medium of claim, wherein each of the plurality of regions of the file system data volume are associated with a first size, the first size corresponding to a number of bits of the first data repository. 
     
     
         16 . The non-transitory computer readable storage medium of  claim 10 , wherein each of the plurality of regions of the file system data volume are associated with a first size that corresponds to a number of bits identified by a user. 
     
     
         17 . An apparatus for maintaining a copy of a data volume, the apparatus comprising:
 a network interface;   a persistent memory   a memory; and   a processor, wherein the processor executing instructions out of the memory:
 creates a first repository for storing file system data that is associated with a file system data volume stored in a persistent memory at a first time; 
 creates a first map that includes a first set of entries that are associated with the file system data volume stored in the persistent memory at the first time, wherein:
 each respective entry of the first set of entries of the first map identify whether a particular region of a plurality of regions of the file system data volume has changed since the first time, and 
 
 prevents the new write to the file system data volume from proceeding based on the identifying that the first region of the file system data volume is still in the initial state; 
 copies data from the first region of the file system data volume to the first data repository; 
 allows the new write to the file system data volume to proceed after the data from the first region of the file system data volume has been copied to the first data repository; and 
 changes a state associated with a first entry in the first map from the initial state to a changed state after the new write to the file system data volume has completed. 
   
     
     
         18 . The apparatus of  claim 17 , wherein:
 a read command is received from a requestor over the network interface;   the processor executing instructions out of the memory:
 identifies that the read command addresses data that is associated with the first region, 
 identifies that data associated with the first region has changed since the first time, and 
 reads the data associated with the read command and with the first region from the first data repository based on the identifying that the data associated with the first region has changed since the first time, and 
   the data associated with the read command and with the first region is provided to the requestor over the network interface.   
     
     
         19 . The apparatus of  claim 18 , wherein the identifying that the data associated with the first region has changed since the first time is identified by accessing the first map and by identifying that the first entry is currently associated with the changed state. 
     
     
         20 . The apparatus of  claim 17 , wherein each of the respective entries of the first set of entries each correspond to a particular number of bits of data of the file system data volume. 
     
     
         21 . The apparatus of  claim 17 , wherein each of the respective entries of the first set of entries each correspond to a particular number of bits of data of the file system data volume.