Efficient space utilization in a flash system using snapshots

Abstract

A method including, responsive to receiving a request identifying a volume and indicating a command to take a snapshot of the volume, mapping a second logical grouping of data to reference the first logical grouping of data, and remapping the first volume to map to the second logical grouping of data instead of the first logical grouping of data such that the first volume remains addressable with similar access permissions before and after creating the snapshot. The method also includes, in response to receiving a write request targeting the second logical grouping, splitting the second logical grouping into a plurality of ranges including a first range and a second range; wherein the first range of the second logical grouping maps to the first logical grouping, and the write request is performed on the second range of the second logical grouping.

What is claimed is: 
     
         1 . A computer system comprising:
 one or more storage devices; and   a storage controller;   wherein the storage controller is configured to:
 in response to receiving a request addressing a volume and indicating a command to take a snapshot of the volume, wherein the volume is mapped to a logical grouping of data: 
 create a second logical grouping of data; 
 map the second logical grouping of data to reference the first logical grouping of data; 
 remap the volume to map to the second logical grouping of data instead of the first logical grouping of data such that the volume remains addressable with similar access permissions before and after creating the snapshot; 
 store an indication that the first logical grouping of data is read-only; and 
 in response to receiving a write request targeting the second logical grouping, split the second logical grouping into a plurality of ranges including a first range and a second range; wherein the first range of the second logical grouping maps to the first logical grouping, and the write request is performed on the second range of the second logical grouping of data. 
   
     
     
         2 . The computer system of  claim 1 , wherein the one or more storage devices are solid state storage devices. 
     
     
         3 . The computer system of  claim 1 , wherein each of the one or more storage devices comprises a flash chip. 
     
     
         4 . The computer system of  claim 1 , wherein the computer system is a flash system. 
     
     
         5 . A method, comprising:
 receiving a request identifying a volume and indicating a command to take a snapshot of the volume, wherein the volume is mapped to a first logical grouping of data; and   responsive to receiving the request:
 creating a second logical grouping of data; 
 mapping the second logical grouping of data to reference the first logical grouping of data; 
 remapping the first volume to map to the second logical grouping of data instead of the first logical grouping of data such that the first volume remains addressable with similar access permissions before and after creating the snapshot; 
 storing an indication that the first grouping of data is read-only; and 
   in response to receiving a write request targeting the second logical grouping, split the second logical grouping into a plurality of ranges including a first range and a second range; wherein the first range of the second logical grouping maps to the first logical grouping, and the write request is performed on the second range of the second logical grouping.   
     
     
         6 . The method of  claim 5 , wherein the a method comprising a method of operation in a flash system. 
     
     
         7 . A non-transitory computer readable storage medium storing program instructions, wherein the program instructions are executable by a processor of a computer system to:
 in response to receiving a request identifying a volume and indicating a command to take a snapshot of the volume, wherein the volume is mapped to a first logical grouping of data:   create a second logical grouping of data;   map the second logical grouping of data to reference the first logical grouping of data;   remap, by the processor, the volume to map the second logical grouping of data instead of the first logical grouping of data such that the volume remains addressable with similar access permissions before and a after creating the snapshot;   store an indication that the first logical grouping of data is read-only; and   in response to receiving a write request targeting the second logical grouping, split the second logical grouping into a plurality of ranges including a first range and a second range; wherein the first range of the second logical grouping maps to the first logical grouping, and the write request is performed on the second range of the second logical grouping.