Date: Thu, 18 Feb 2010 19:19:54 -0800 From: Matt Reimer <mattjreimer@gmail.com> To: Dan Naumov <dan.naumov@gmail.com> Cc: FreeBSD-STABLE Mailing List <freebsd-stable@freebsd.org>, rnoland@freebsd.org Subject: Re: booting off a ZFS pool consisting of multiple striped mirror vdevs Message-ID: <f383264b1002181919k5e624c05t84e5f8bc02767093@mail.gmail.com> In-Reply-To: <cf9b1ee01002181636y5776968cn1e8c49deae7e8311@mail.gmail.com> References: <cf9b1ee01002160038o25e17bc8sd54e66be7c67f859@mail.gmail.com> <f383264b1002181057y48e56cebv1c8bbb1c0fe9d1d2@mail.gmail.com> <f383264b1002181503q74d1fc95y470f11be49c11d2f@mail.gmail.com> <cf9b1ee01002181636y5776968cn1e8c49deae7e8311@mail.gmail.com>
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On Thu, Feb 18, 2010 at 4:36 PM, Dan Naumov <dan.naumov@gmail.com> wrote: > > A stripe of 3-way mirrors, whoa. Out of curiosity, what is the system > used for? I am not doubting that there exist some uses/workloads for a > system that uses 6 disks with 2 disks worth of usable space, but > that's a bit of an unusual configuration. What are your system/disc > specs and what kind of performance are you seeing from the pool? > It's for a reasonably busy webserver hosting a few hundred domains, which tends to be somewhat seek-intensive. For this pool we had two main criteria: speed and double-disk redundancy. A stripe of three two-way mirrors would only give us single-disk redundancy in the worst case (i.e. losing both disks in one of the mirrors), so we went with two three-way mirrors instead. Even though we're only getting the capacity of two disks worth of space, we'll still have 6x the capacity of the array it's replacing. A simple-minded dd test gives me ~180MB/s writing a single long file, and 400-500MB/s reading. Matt
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