Compression

[guldan]

Hey Guys,

I enabled the highest compression for my backup disk and im transferring stuff over.. it doesn't seem to be any smaller. anyway I can check that it's working properly?

 

[William Grzybowski]

# zfs get refcompressratio tank

 

[guldan]

# zfs get refcompressratio tank

It says 1.02x but in Freenas I set it for Maximum on the entire disk, shouldn't it be higher?

 

[Stephens]

That depends on what you're sending over. Already compressed data doesn't gain much (if anything) from compression. And it's not like FreeNAS is using the most comprehensive compression available. It is, after all, doing it on the fly.

 

[William Grzybowski]

Depends on the type of file you're compressing? What are those? audio/video? :)

 

[guldan]

Depends on the type of file you're compressing? What are those? audio/video? :)

So far pictures, mostly JPGs and MP3s which I realize are compressed but I figure it would compress them a bit more than 1.02x

What is the process it uses? when you dump say.. an MP3 into a ZFS compressed drive with GZIP. Does every file get "GZIPPED" immediately during transfer?

 

[JaimieV]

You shouldn't expect any notable amount of compression on compressed image files (like jpg), compressed audio (like mp3), or movies (pretty much any!) - all of them are already compressed with media specific compression mechanisms and will not squeeze any further.

If they did, the creators of the various encoding standards would have included an extra step to do just that.