Atomic cache transactions in a distributed storage system

Abstract

An atomic write data structure is provided comprising a stripe buffer list descriptor defining state information of a stripe buffer list entry associating a virtual stripe of data storage space with cache data. An associated method is provided comprising constructing metadata associating a virtual stripe of data storage space with cache data; modifying the metadata to reflect state changes related to a pending data transaction between the data storage space and the cache; writing the modified metadata to an atomic write descriptor; and recalling the atomic write descriptor for transacting a selected atomic block size in an event of an interruption while executing the data transaction.

1 . An atomic write data structure comprising a stripe buffer list descriptor defining state information of a stripe buffer list entry associating a virtual stripe of data storage space with cache data.  
     
     
         2 . The data structure of  claim 1  comprising a block indicator defining a number of blocks in a pending data transaction between the storage space and the cache.  
     
     
         3 . The data structure of  claim 2  comprising an offset indicator defining a starting address of the number of blocks in the data buffer.  
     
     
         4 . The data structure of  claim 3  comprising a first index to a first stripe buffer list entry associated with a state of the respective stripe after the data transaction.  
     
     
         5 . The data structure of  claim 4  comprising a second index to a second stripe buffer list entry associated with a state of the respective stripe before the data transaction.  
     
     
         6 . The data structure of  claim 5  comprising a condition indicator defining a characteristic type of pending data transaction.  
     
     
         7 . The data structure of  claim 6  wherein the condition indicator defines a characteristic type of data transaction from a set consisting of a miss sequence, a previous dirty sequence, and a random array of independent drives update parity sequence.  
     
     
         8 . A method comprising: 
 constructing metadata associating a virtual stripe of data storage space with cache data;    modifying the metadata to reflect state changes related to a pending data transaction between the data storage space and the cache;    writing the modified metadata to an atomic write descriptor; and    recalling the atomic write descriptor for transacting a selected atomic block size in an event of an interruption while executing the data transaction.    
     
     
         9 . The method of  claim 8  wherein the writing step is characterized by writing a block indicator defining the number of data blocks in the transaction.  
     
     
         10 . The method of  claim 8  wherein the writing step is characterized by writing an offset indicator defining a starting address of the number of data blocks in the data buffer.  
     
     
         11 . The method of  claim 8  wherein the constructing step comprises defining a stripe buffer list aligning the virtual stripes of the data storage space to the cache data, and wherein the writing step comprises defining a first index to a first stripe buffer list entry associated with a state of the respective stripe after the data transaction.  
     
     
         12 . The method of  claim 11  wherein the writing step comprises defining a second index to a second stripe buffer list entry associated with a state of the respective stripe before the data transaction.  
     
     
         13 . The method of  claim 12  wherein the writing step comprises defining a condition indicator relating to a characteristic type of data transaction.  
     
     
         14 . The method of  claim 12  wherein the writing step is characterized by updating state information of parity data in a redundant array of independent drives.  
     
     
         15 . The method of  claim 12  wherein the writing step is characterized by updating state information of dirty data previously existing in the cache.  
     
     
         16 . The method of  claim 12  wherein the writing step is characterized by updating a bit map relating locations of dirty data within the data buffer sectors.  
     
     
         17 . The method of  claim 12  wherein the writing step is characterized by updating a bit map relating locations of present data within the data buffer sectors.  
     
     
         18 . A method of executing data transactions in a distributed storage system comprising defining data structures associating cache data with a stripe of a virtual data storage capacity.  
     
     
         19 . The method of  claim 18  wherein the defining step comprises storing a condition indicator that deterministically branches a sequence of execution steps in relation to a characteristic type of pending data transaction.  
     
     
         20 . The method of  claim 18  wherein the sequence of execution steps is completed idempotently if an interruption condition occurs during execution and the condition is not idle, and wherein the condition is cleared after completion of the execution.