Selective compression in data storage systems

1. A method for selectively compressing data in a data storage system, the method comprising:

arranging data storage system cache memory into multiple input/output (IO) cache macroblocks, wherein a first set of IO cache macroblocks are configured as compressed IO cache macroblocks, each compressed IO cache macroblock storing a plurality of variable sized compressed IO data blocks, and a second set of IO cache macroblocks are configured as non-compressed IO cache macroblocks, each non-compressed IO cache macroblock storing a plurality of fixed sized non-compressed IO data blocks, wherein the first and second set of IO cache macroblocks are stored in memory as contiguous segments having a fixed size;

determining IO activity level of IO data blocks stored in IO cache macroblocks;

creating a plurality of macroblock groups, wherein each macroblock group corresponds to a particular IO activity range;

arranging IO data blocks into of the macroblock groups according to the IO activity range that corresponds to the data block IO activity level;

compressing each macroblock group, wherein compressing includes selecting a software compression algorithm based on the IO activity range of the macroblock group; and

writing the macroblocks to corresponding macroblocks in persistent storage.

2. The method of claim 1 , wherein creating the macroblock groups includes creating macroblocks that correspond to data block content.

3. The method of claim 2 , wherein the data block content is text associated with a text file.

4. The method of claim 1 , wherein arranging IO data blocks includes arranging IO data blocks into a macroblock belonging to a macroblock category according to data block content.