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Date: Fri, 23 May 2014 15:10:01 GMT
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From: Allan Jude <allanjude@freebsd.org>
Subject: Re: docs/139336: [request] ZFS documentation suggestion
Reply-To: Allan Jude <allanjude@freebsd.org>
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The following reply was made to PR docs/139336; it has been noted by GNATS.

From: Allan Jude <allanjude@freebsd.org>
To: bug-followup@FreeBSD.org, zdbs@lif.de
Cc:  
Subject: Re: docs/139336: [request] ZFS documentation suggestion
Date: Fri, 23 May 2014 11:05:01 -0400

 ZFS compression is completely transparent, so the OS and applications
 running on top of it are unaware of it. It is safe to compress any files
 on your system.
 
 With the new LZ4 option in ZFS v5000 (FreeBSD 9.2, 8.4 and 10.0 or
 later), the overhead of the compression is much smaller. In addition to
 being able to compress at 500mb/s/core and decompress at 1500mb/s/core
 on a low end i3 laptop processor, LZ4 also has an 'early abort' feature,
 where if the compression ratio of the block is less than 12.5% after the
 first ms of attempting to compress it, it aborts and writes the block
 uncompressed. This means it will not waste a lot of CPU time trying to
 compress already compressed files like .tar.gz or .mp3
 
 This is documented here:
 http://www.allanjude.com/zfs_handbook/zfs-term.html#zfs-term-compression
 
 And should be committed to the handbook shortly.
 
 -- 
 Allan Jude