Date: Wed, 12 Oct 2011 14:39:40 -0500 (CDT) From: Bob Friesenhahn <bfriesen@simple.dallas.tx.us> To: Jeremy Chadwick <freebsd@jdc.parodius.com> Cc: freebsd-fs@freebsd.org Subject: Re: ZFS/compression/performance Message-ID: <alpine.GSO.2.01.1110121435130.9971@freddy.simplesystems.org> In-Reply-To: <20111012165126.GA26562@icarus.home.lan> References: <alpine.BSF.2.00.1110111710210.12895@Elmer.dco.penx.com> <j73vl7$v02$1@dough.gmane.org> <CAHHaOua7zwp4DCgcU4bSFG2d-Kz-j_ovV7YiSMqmy700wFjBHg@mail.gmail.com> <20111012165126.GA26562@icarus.home.lan>
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On Wed, 12 Oct 2011, Jeremy Chadwick wrote: > > 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.. Solaris solved the problem by putting the zfs writer threads into a special scheduling class so that they are usually lower priority than normal processing. Before this change, a desktop system would become almost unusable (intermittent loss of keyboard/mouse) while writing lots of data with compression enabled. Some NFS servers encountered severe enough issues that NFS clients reported NFS timeouts. > 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. >From what you describe, Solaris must be doing much better in this regard than FreeBSD. Solaris is not necessarily faster but there is now little impact on interactive tasks. Bob -- Bob Friesenhahn bfriesen@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/
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