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Date: Mon, 25 Nov 2013 10:18:30 -0800
Message-ID: <CAOjFWZ5cDj2EVzft23vogUtv4jGSGM3RdL0wT_JfHjO-fgg-yw@mail.gmail.com>
Subject: Re: Performance difference between UFS and ZFS with NFS
From: Freddie Cash <fjwcash@gmail.com>
To: Eric Browning <ericbrowning@skaggscatholiccenter.org>
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On Mon, Nov 25, 2013 at 10:14 AM, Eric Browning <
ericbrowning@skaggscatholiccenter.org> wrote:

> I am using /dev/zero
>
> /usr/bin/time -h dd if=3D/dev/zero of=3Dsometestfile bs=3D1024 count=3D30=
00000
>

You really shouldn't use /dev/zero to "benchmark" ZFS.  It doesn't work the
way you think it will, especially if dedupe or compression are enabled.

Either use a proper filesystem benchmarking tool like iozone or bonnie++ or
fio; or create a big file using /dev/random and then dd that file to
various places in the filesystem.=E2=80=8B=E2=80=8B

# =E2=80=8Bdd if=3D/dev/random of=3Dbigfile.100M bs=3D1M count=3D100=E2=80=
=8B

=E2=80=8BReboot to clear caches.  Then use if=3Dbigfile.100M in your actual=
 testing.=E2=80=8B


--=20
Freddie Cash
fjwcash@gmail.com