Date: Fri, 16 Sep 2011 09:57:45 -0400 From: freebsd@top-consulting.net To: "freebsd-questions@freebsd.org" <freebsd-questions@freebsd.org> Subject: Re: FS of choice for max random iops ( Maildir ) Message-ID: <20110916095745.872947fg6vym1vy8@mail.top-consulting.net> In-Reply-To: <32990703-D068-4B0D-AF3A-C1E6EA0A4100@elde.net> References: <20110916063153.200375qdq59crf8c@mail.top-consulting.net> <32990703-D068-4B0D-AF3A-C1E6EA0A4100@elde.net>
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Quoting Terje Elde <terje@elde.net>: > On 16. sep. 2011, at 12:31, freebsd@top-consulting.net wrote: >> Right now I defined an entire array of 8TB ( all 16 disks ) >> separated in two pieces. 50 GB for FreeBSD to boot and the rest >> available to configure as storage. > > ZFS will want to write to it's ZIL (zfs intent log) before writing > to the final location of the data. Even if you're not waiting for > the ZIL-write to disk (because of the controller ram), those writes > will probably make it through to disk. That gives you twice as many > writes to disk, and a lot more seek. > > If you want to take zfs for a proper spin, I'd like to sugget adding > two small SSDs to the setup, mirrored by zfs. You can use those both > for the ZIL, and also as cache, for the array. That's a fairly small > investment these days, and I would be surprised if it didn't > significantly improve performance, both for your benchmark, and real > load. > > Note: you might be in trouble if you loose your ZIL, thus the > doubling up. I *think* you can SSD a cache without risking dataloss, > but don't take my word for it. > > Terje I know it's usually a big no-no but since I have the battery backed-up write cache from the raid card, can't I just disable the ZIL entirely ?
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