Date: Mon, 7 Jun 2010 12:12:16 +0100 From: Martin Simmons <martin@lispworks.com> To: freebsd-fs@freebsd.org Subject: Re: zfs i/o error, no driver error Message-ID: <201006071112.o57BCGMf027496@higson.cam.lispworks.com> In-Reply-To: <20100607090850.GA49166@icarus.home.lan> (message from Jeremy Chadwick on Mon, 7 Jun 2010 02:08:50 -0700) References: <4C0CAABA.2010506@icyb.net.ua> <20100607083428.GA48419@icarus.home.lan> <4C0CB3FC.8070001@icyb.net.ua> <20100607090850.GA49166@icarus.home.lan>
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>>>>> On Mon, 7 Jun 2010 02:08:50 -0700, Jeremy Chadwick said:
>
> I'm still trying to figure out why people do this.
Maybe because the ZFS Best Practices Guide suggests it? ("Run zpool scrub on
a regular basis to identify data integrity problems...")
It makes sense to detect errors when there is still a healthy mirror, rather
than waiting until two drives are failing :-)
> It's important to remember that scrubs are *highly* intensive on both
> the system itself as well as on all pool members. Disk I/O activity is
> very heavy during a scrub; it's not considered "normal use".
Is it worse that a full backup? I guess scrub does read all drives, but OTOH
backup will typically read all data non-linearly, which adds a different kind
of stress.
__Martin
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