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Date: Wed, 6 May 2009 12:24:11 -0700
From: Andrew Sharp <andy.sharp@onstor.com>
To: Narayan Venkat <narayan.venkat@onstor.com>
Subject: compression comparison (WIP) so far
Message-ID: <20090506122411.0a53873d@ripper.onstor.net>
Organization: Onstor
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N,

I thought I would show you what I have right now.  As you can see, the
ZFS numbers look terrible, except for the compression ratio, which
ain't bad at all.  But I don't want to put any numbers out into the
world yet until I have gigabit results, because as you know, numbers
never go away, but do get confused and misrepresented.



I took our dev branch, deleted already compressed files like gifs,
jpegs, debs, rpms, .gz and so forth, and copied that to a leopard
fileset with gzip-6 enabled.  Twenty times.  Original single copy is
2-ish GB (1930.86 MiB), and ZFS is reporting 3.16:1 compression ration.
Math is reporting 3.04:1, so now we know ZFS lies, but what else
is new. ~:^)

Average copy time: 2542.2455s ==> 777.74 KiB/s
Mean copy time:    2535.1850s ==> 779.90 KiB/s

To a standard, uncompressed fileset:

Average copy time: 2415.595s  ==> 818.51 KiB/s
Mean copy time:    XXXX.YYYs  ==> XXX.YY KiB/s


For comparison purposes, the exact same operation to mightydog
(actually running concurrently with a leopard copy):

Copy time:           563.669s ==> 3.4255 MiB/s

Similar test on a btrfs filesystem, no raid or anything, regular gzip
compression, on a 5400RPM IDE laptop drive connected via USB: (I think
this is a 10 year old drive that has 500KiB cache!)

Average copy time:    91.49s  ==> 21.10 MiB/s
Mean copy time:       93.82s  ==> 20.58 MiB/s

Btrfs with no compression:

Average copy time:   206.211s  ==> 9.36 MiB/s
Mean copy time:      207.985s  ==> 9.28 MiB/s

So, as you can see, using btrfs and compression doubles the speed of a USB drive!

