Date: Fri, 17 Sep 2010 09:37:32 -0700 From: Jeremy Chadwick <freebsd@jdc.parodius.com> To: Freddie Cash <fjwcash@gmail.com> Cc: freebsd-fs@freebsd.org Subject: Re: what happens to pool if ZIL dies on ZFS v14 Message-ID: <20100917163732.GA59537@icarus.home.lan> 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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On Fri, Sep 17, 2010 at 09:21:54AM -0700, Freddie Cash 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. I was under the impression ZFS still managed to utilise the ZIL when a pool didn't have any "log" devices associated with it (possibly some sort of statically-allocated amount of RAM?) You can search the FreeBSD lists for people continually advocating vfs.zfs.zil_disable=1. There's even a couple blog posts from engineers talking about how the only way to get their filers to behave decently was to disable the ZIL[1][2][3]. In most (every?) cases I've seen where someone advocates disabling the ZIL, pool details aren't provided, which leads me to believe their pools have no "log" devices. Here's a better way to phrase my question: does vfs.zfs.zil_disable=1 do anything if there aren't any "log" devices in use (in any pool)? [1]: http://jmlittle.blogspot.com/2010/03/zfs-log-devices-review-of-ddrdrive-x1.html [2]: http://blogs.sun.com/erickustarz/entry/zil_disable [3]: http://weblog.etherized.com/posts/130 -- | Jeremy Chadwick jdc@parodius.com | | Parodius Networking http://www.parodius.com/ | | UNIX Systems Administrator Mountain View, CA, USA | | Making life hard for others since 1977. PGP: 4BD6C0CB |
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