Date: Mon, 11 Jan 2010 15:29:54 -0800 From: "K. Macy" <kmacy@freebsd.org> To: Dan Naumov <dan.naumov@gmail.com> Cc: freebsd-fs@freebsd.org, Damian Gerow <dgerow@afflictions.org>, FreeBSD-STABLE Mailing List <freebsd-stable@freebsd.org> Subject: Re: ZFS on top of GELI Message-ID: <82c4140e1001111529u7d7ac409h63dda4cc10b76522@mail.gmail.com> In-Reply-To: <cf9b1ee01001101128v5d636ab6p1fa3e5bcc713273d@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>
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>> >> If performance is an issue, you may want to consider carving off a parti= tion >> on that SSD, geli-fying it, and using it as a ZIL device. =A0You'll prob= ably >> see a marked performance improvement with such a setup. > > That is true, but using a single device for a dedicated ZIL is a huge > no-no, considering it's an intent log, it's used to reconstruct the > pool in case of a power failure for example, should such an event > occur at the same time as a ZIL provider dies, you lose the entire > pool because there is no way to recover it, so if ZIL gets put > "elsewhere", that elsewhere really should be a mirror and sadly I > don't see myself affording to use 2 SSDs for my setup :) > This is false. The ZIL is used for journalling synchronous writes. If your ZIL is lost you will lose the data that was written to the ZIL, but not yet written to the file system proper. Barring disk corruption, the file system is always consistent. -Kip
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