what happens to pool if ZIL dies on ZFS v14

[Gil Vidals]

First, let me say that I'm receiving excellent input from the FreeBSD
community. I'm new to FreeBSD and ZFS and this mailing list has been very
helpful.

I'm running ZFSv14 on FreeBSD 8.1 AMD64 with 8GB of DDR3 RAM with two SSDs -
one for the ZIL and the other for the L2ARC cache.

zambia# zpool iostat -v 1 1
                     capacity     operations    bandwidth
pool               used  avail   read  write   read  write
----------------  -----  -----  -----  -----  -----  -----
tank              6.57G   921G      0     11   116K   438K
  mirror          6.57G   921G      0      5   116K   229K
    label/disk1       -      -      0      3  57.9K   229K
    label/disk2       -      -      0      3  57.8K   229K
  label/zilcache   136K  59.5G      0      6     17   209K
cache                 -      -      -      -      -      -
  label/l2cache   59.6G  8.50K      0      0  31.5K  48.9K
----------------  -----  -----  -----  -----  -----  -----

Observing the ZIL Cache, I see it being used very sparingly. And now that I
know the SSD slog must be mirrored in ZFS < v19, I think the best course of
action (assuming I'm not buying more equipment) is to mirror the ZIL SSD and
abandon the L2ARC altogether. Won't RAM be used for L2ARC instead?

--Gil Vidals / VMRacks.com

On Fri, Sep 17, 2010 at 9:21 AM, Freddie Cash <fjwcash at gmail.com> wrote:

> On Fri, Sep 17, 2010 at 9:18 AM, Jeremy Chadwick
> <freebsd at jdc.parodius.com> wrote:
> > On Fri, Sep 17, 2010 at 09:17:11AM -0700, Freddie Cash wrote:
> >> On Fri, Sep 17, 2010 at 8:35 AM, Gil Vidals <gvidals at gmail.com> wrote:
> >> > Bryan thank you for the detailed answer.
> >> >
> >> > Assuming the ZIL SSD died, what steps would I follow to recover the
> pool? (i
> >> > hope it is recoverable).
> >>
> >> If you are running ZFSv1 through ZFSv18 and your log device dies, your
> >> pool is dead, gone, unrecoverable, no secret prize, no continues, do
> >> not pass go, etc, etc, etc.
> >>
> >> If you are running ZFSv19 or newer and your log device dies, you can
> >> remove the dead device and carry on.  You will lose any data that was
> >> in the ZIL, but the pool will be intact.
> >
> > Given the severity of this predicament, then why is it people are
> > disabling the ZIL (via vfs.zfs.zil_disable=1) ?
>
> I'm not sure what you mean by that.
>
> This (dead ZIL == dead pool) only applies to separate log (slog) devices.
>
> --
> Freddie Cash
> fjwcash at gmail.com
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