On Sep 20, 2011 8:38 AM, "Edward Ned Harvey" <lop...@nedharvey.com> wrote:

>
> As for mirroring the ZIL:  Distrust for a single drive has some truth in
it.
> If you have a disk failure (including data error) on your unmirrored ZIL
> device, which coincides with a system ungraceful crash, then the data on
> that device would be lost.  The assumption, if you don't mirror your ZIL,
is
> that the probability of these multiple failures coinciding is small enough
> to be comparable to the probability of multiple disk failures coinciding.
>
>
It used to be that if you didn't mirror the ZIL and had it go bad that you
had a major failure condition and you would have to recreate the spool from
scratch. Granted, this was a pretty silly limitation and was fixed in 2010.
Now, if you lose the zip it will fail back to the spool disks.  Still, since
I'm already mirroring the OS, I get ZIL  mirroring essentially free. The ZIL
is only used for writing unless there is a crash.
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