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Storage Efficiency – Compression

Storage Compression is one of those efficiency feature that isn’t talked about much. There are lots of ways in which you can implement compression like File System compression, storage array based compression, backup data compression etc. Storage Compression coupled with thin provisioning in CLARiiON/VNX Systems provide thin provisioned pools the much needed Space Reclamation capability that allows white space to be reclaimed. Remember one of the down side of implementing thin Provisioning for Server Virtualization environment was the thin space reclamation and Storage compression exactly brings that capability for the EMC CLARiiON/VNX arrays.

Data written on LUNs are compressed based on meeting set thresholds/parameters. Generally runs as background task. When host reads compressed data, compressed data is decompressed in the Memory and made available to the host. A LUN when enabled for Compression becomes thin provisioned as well. Freed thin-LUN block space is made available for allocation at a storage pool level. Compression is best suited for data luns that contains whitespaces or recurring patterns.

In EMC Arrays, when we enable compression on a LUN, Complete LUN processing is carried out after which data is processed in fixed 64KB increments encoding any recurring strings within data currently being processed and then moves on to next 64 KB increment. If the resulting savings is less than 8 KB, the data would be written in uncompressed format. If the System can free up to 1 GB of 8 KB blocks on a LUN, the space would be returned back to the Storage Pool as free space.  NetApp uses 32K compression groups for scanning.

Most data stored on disk today has at least some redundancy and is easily compacted and lot of space can be reclaimed. Based on my experience at the least 10& of space can be reclaimed but based on data type the value can even go higher.

I have talked of EMC array compression as I have worked on them and pretty much felt the ease of use and its benefits but should pretty much the same with all other supported Storage arrays. Please go through the Vendor documentation for in-depth details and start compressing your data now!

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  1. Sham
    March 7, 2013 at 12:38 pm

    Impressive info

  1. March 4, 2013 at 9:29 pm

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