Date: Tue, 20 Feb 2007 02:47:00 -0500 From: "Zaphod Beeblebrox" <zbeeble@gmail.com> To: freebsd-hackers@freebsd.org Subject: Fwd: Abyssmal dump cache efficiency Message-ID: <5f67a8c40702192347h7383a238v2ff212b38404eb70@mail.gmail.com> In-Reply-To: <5f67a8c40702192346re1ada13gcfb3d10db6139cde@mail.gmail.com> References: <20070218002758.GQ859@turion.vk2pj.dyndns.org> <5f67a8c40702192346re1ada13gcfb3d10db6139cde@mail.gmail.com>
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(oops... didn't group reply) ---------- Forwarded message ---------- From: Zaphod Beeblebrox <zbeeble@gmail.com> Date: Feb 20, 2007 2:46 AM Subject: Re: Abyssmal dump cache efficiency To: Peter Jeremy <peterjeremy@optushome.com.au> On 2/17/07, Peter Jeremy <peterjeremy@optushome.com.au> wrote: > > > I've tried modelling a unified cache along the NetBSD line and there > appears to be a massive improvement in cache performance. It's unclear > how much of an improvement this will give in overall performance but > not physically reading data from disk must be faster than reading it. > > I believe it would be worthwhile creating a todo item to investigate > this more thoroughly. This squares perfectly with my recent observation that while runing some combination of "dump | restore" that the dump disks incur 2 to 3 times more I/O (reading) than the restore disks. Now... for "performance" I was using the cache function --- maybe the cache is actually a detriment.
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