Date: Wed, 12 Oct 2011 09:51:26 -0700 From: Jeremy Chadwick <freebsd@jdc.parodius.com> To: freebsd-fs@freebsd.org Subject: Re: ZFS/compression/performance Message-ID: <20111012165126.GA26562@icarus.home.lan> In-Reply-To: <CAHHaOua7zwp4DCgcU4bSFG2d-Kz-j_ovV7YiSMqmy700wFjBHg@mail.gmail.com> References: <alpine.BSF.2.00.1110111710210.12895@Elmer.dco.penx.com> <j73vl7$v02$1@dough.gmane.org> <CAHHaOua7zwp4DCgcU4bSFG2d-Kz-j_ovV7YiSMqmy700wFjBHg@mail.gmail.com>
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On Wed, Oct 12, 2011 at 09:37:10AM -0700, David Brodbeck wrote: > On Wed, Oct 12, 2011 at 5:02 AM, Johannes Totz <jtotz@imperial.ac.uk> wrote: > > > I just did a simple write test yesterday: > > > > 1) 6 MB/sec for gzip, 1.36x ratio > > 2) 34 MB/sec for lzjb, 1.23x ratio > > > > I'll stick with lzjb. It's good enough to get rid of most of the > > redundancy and speed is acceptable. > > > > That's what we use on our text-heavy filesystems on our OpenSolaris server. > (We work with large text corpora, so we have hundreds of gigabytes of pure > text.) My benchmarks showed the performance hit for reads is nonexistent > when viewed over NFS, and the performance hit for writes is relatively > small...plus we don't write to that filesystem much. We see about 1.5x > compression overall, with a little over 2x on some datasets that are > particularly compressible. That might be the case on OpenSolaris but the performance hit on FreeBSD RELENG_8 is very high -- enough that enabling compression (using the defaults) causes stalls when I/O occurs (easily noticeable across SSH; characters are delayed/stalled (not buffered)), etc.. The last time I tried it on RELENG_8 was right after ZFSv28 was MFC'd. If things have improved I can try again (I don't remember seeing any commits that could affect this), or if people really think changing the compression model to lzjb will help. Another point: I haven't tinkered with compression on our Solaris 10 machines at work so I don't know if it performs better, equal, or worse than FreeBSD or OpenSolaris. -- | Jeremy Chadwick jdc at parodius.com | | Parodius Networking http://www.parodius.com/ | | UNIX Systems Administrator Mountain View, CA, US | | Making life hard for others since 1977. PGP 4BD6C0CB |
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