Date: Tue, 16 Oct 2012 13:25:57 +0200 From: Olivier Smedts <olivier@gid0.org> To: Dustin Wenz <dustinwenz@ebureau.com> Cc: freebsd-fs@freebsd.org Subject: Re: Imposing ZFS latency limits Message-ID: <CABzXLYNaaKtfGf11%2Bm5td0G8kw8KT7TR-7LCHyFdxeKiw5AfxA@mail.gmail.com> In-Reply-To: <6116A56E-4565-4485-887E-46E3ED231606@ebureau.com> References: <6116A56E-4565-4485-887E-46E3ED231606@ebureau.com>
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2012/10/8 Dustin Wenz <dustinwenz@ebureau.com>:
> I'm trying to find a way to get lower read latency in ZFS when there is a=
failing disk in a mirror. The specific failure mode that I'm trying to han=
dle is when a disk takes significantly longer than usual to respond to read=
requests, but is not so far gone that the OS drops it from the bus. In tha=
t case, the whole pool can become much less responsive than I think it need=
s to be.
>
> Since ZFS has access to the data I'm reading through other members in a m=
irror, I would like ZFS to defer to the redundant disks when individual dis=
k latency exceeds some threshold that I would define. Is there any provisio=
n for this in the FreeBSD ZFS implementation?
That would be great - no need for TLER drives. But if you want to
"drop" the drive from the bus, that would be a GEOM thing. Don't know
if that's possible to implement.
--=20
Olivier Smedts _
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