Date: Fri, 17 Sep 2010 09:47:32 -0700 From: Gil Vidals <gvidals@gmail.com> To: freebsd-fs@freebsd.org Subject: Re: what happens to pool if ZIL dies on ZFS v14 Message-ID: <AANLkTimd6ZKENg3-W-1DxOoR5mRcTb0mfRikznKWuBTD@mail.gmail.com> In-Reply-To: <AANLkTi=NX6koyj_xmadrTw8OvgCATPA=EQnTPmAxNGpo@mail.gmail.com> References: <AANLkTi=vYVG300nhMjkcLju=kQhBdPJDqyaXR0mG84%2Bp@mail.gmail.com> <4C9385B0.2080909@shatow.net> <AANLkTin0LwQz%2BWi5cBOcHuVqyOz3%2BfFR7YC_=f2L5CyX@mail.gmail.com> <AANLkTinbPK1rNK5hg=t7N=sqFLuh8sNrZT9DFC_ppXWF@mail.gmail.com> <20100917161847.GA58503@icarus.home.lan> <AANLkTi=NX6koyj_xmadrTw8OvgCATPA=EQnTPmAxNGpo@mail.gmail.com>
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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@gmail.com> wrote:
> On Fri, Sep 17, 2010 at 9:18 AM, Jeremy Chadwick
> <freebsd@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@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@gmail.com
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