Date: Tue, 12 Jan 2010 09:20:43 +0100 From: Gerrit =?ISO-8859-1?Q?K=FChn?= <gerrit@pmp.uni-hannover.de> To: kmacy@freebsd.org Cc: freebsd-fs@freebsd.org Subject: Re: ZFS on top of GELI Message-ID: <20100112092043.d1370d55.gerrit@pmp.uni-hannover.de> In-Reply-To: <82c4140e1001111529u7d7ac409h63dda4cc10b76522@mail.gmail.com> References: <cf9b1ee01001100708m7851418cmbb77cc3580d0fab3@mail.gmail.com> <20100110161206.GA86684@plebeian.afflictions.org> <cf9b1ee01001101019o51e9a52fi6d02905914508706@mail.gmail.com> <20100110184612.GC86684@plebeian.afflictions.org> <cf9b1ee01001101128v5d636ab6p1fa3e5bcc713273d@mail.gmail.com> <82c4140e1001111529u7d7ac409h63dda4cc10b76522@mail.gmail.com>
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On Mon, 11 Jan 2010 15:29:54 -0800 "K. Macy" <kmacy@freebsd.org> wrote about Re: ZFS on top of GELI: KM> > That is true, but using a single device for a dedicated ZIL is a huge KM> > no-no, considering it's an intent log, it's used to reconstruct the KM> > pool in case of a power failure for example, should such an event KM> > occur at the same time as a ZIL provider dies, you lose the entire KM> > pool because there is no way to recover it, so if ZIL gets put KM> > "elsewhere", that elsewhere really should be a mirror and sadly I KM> > don't see myself affording to use 2 SSDs for my setup :) KM> This is false. The ZIL is used for journalling synchronous writes. If KM> your ZIL is lost you will lose the data that was written to the ZIL, KM> but not yet written to the file system proper. Barring disk KM> corruption, the file system is always consistent. So how would ZFS behave if ZIL is sitting on a single disk that is then lost? Throw away the intented writes and continue happily from there on? I still have some broken volume sitting around that panics the kernel when trying to replay the (obviously somehow corrupted) ZIL (see <http://www.freebsd.org/cgi/query-pr.cgi?pr=kern/140433>) and I wonder if situations like this could be handled by taking out the ZIL drive (only if there is a dedicated one, of course). cu Gerrit
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