Date: Tue, 23 Oct 2012 10:40:16 -0500 From: Dustin Wenz <dustinwenz@ebureau.com> To: "<freebsd-fs@freebsd.org>" <freebsd-fs@freebsd.org> Subject: Re: Imposing ZFS latency limits Message-ID: <2CB1D556-1EAF-43F9-8A24-36548C663ED8@ebureau.com> In-Reply-To: <op.wmk0phab34t2sn@tech304> References: <6116A56E-4565-4485-887E-46E3ED231606@ebureau.com> <CABzXLYNaaKtfGf11%2Bm5td0G8kw8KT7TR-7LCHyFdxeKiw5AfxA@mail.gmail.com> <op.wl9vj0os34t2sn@tech304> <089898A4493042448C934643FD5C3887@multiplay.co.uk> <op.wmk0phab34t2sn@tech304>
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On Oct 22, 2012, at 8:21 AM, Mark Felder <feld@feld.me> wrote: > On Tue, 16 Oct 2012 10:46:00 -0500, Steven Hartland = <killing@multiplay.co.uk> wrote: >=20 >>=20 >> Interesting, what metrics where you using which made it easy to = detect, >> work be nice to know your process there Mark? >=20 > One reason is that our virtual machine performance gets awful and we = get alerted for higher than usual load and/or disk io latency by the = hypervisor. Another thing we've implemented is watching for some SCSI = errors on the server too. They seem to let us know before it really gets = bad. >=20 > It's nice knowing ZFS is doing everything within its power to read the = data off the disk, but when there's a fully intact raidz it should be = smart enough to kick a disk out that's being problematic. What hypervisor are you using? Is it with a passive JBOD? There are other situations where a disk is not failing that you may not = get constant read performance, such as when a disk is undergoing thermal = recalibration, being scanned for diagnostics, etc. Any sort of realtime = database or streaming application could benefit from better latency = control. It's possible that we have no control over this, and are subject to = whatever features Oracle decides to include or omit from ZFS. - .Dustin
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