ZFS compression types

ZFS compression as of OpenSolaris 2008.11 has a few types to choose from.

lzjb (default) | gzip | gzip-[1-9]

They are used via the zfs set compression=gzip poolname command.

The following test was quickly done out of personal interest – and is in no way scientific!

I have a AMD cpu with 3 cores (2.4Ghz). The data i copied to each of the shares consisted of video / documents / pictures and music. The first test i have done is based on compression only (i have not measured throughput)

Original Data Size : 412MB

lzjb : 312MB Compression ratio : 1.32

gzip : 293MB Compression ratio : 1.41

gzip9 : 292MB Compression ratio : 1.41

gzip is the winner on compression. With this small sample of data it is unclear if the extra CPU overhead on a gzip-9 zfs files system is worth it – from these results i would say it isn’t.

Again – gzip may be the winner on compression, but this does not reflect an improvement on throughput (untested).

Update: i’ve done a quick test on cpu load and throughput and i wouldnt recommend using gzip unless you are really limited on disk space – or have plenty of CPU to spare. lzjb is much faster (less load on cpu) and does a pretty good job for compression on the fly.

08/06/2011 Update

If you want to check the compression on a particular file you can use a combination of ls (true files size) and du (size after compression) like so…

actual size

ls -lh file*

Compressed size

du -hs file*

 

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  1. Pingback: ZFS basics | Daz's Bits and Bobs

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