Date: Fri, 16 Sep 2011 10:18:33 -0400 From: freebsd@top-consulting.net Cc: freebsd-questions@freebsd.org Subject: Re: FS of choice for max random iops ( Maildir ) Message-ID: <20110916101833.17485ybnq5srjbc4@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 Well, I tried disabling the ZIL on a new dataset. These are the commands that I ran: zpool create data da1 zfs create data/maildomains zfs set sync=disabled data/maildomains dd bs=1024 if=/dev/zero of=/data/maildomains/t1 count=1M 1048576+0 records in 1048576+0 records out 1073741824 bytes transferred in 14.537711 secs (73859071 bytes/sec) Got a measly 74MB/sec. On the UFS partition however... dd bs=1024 if=/dev/zero of=/usr/t1 count=1M 1048576+0 records in 1048576+0 records out 1073741824 bytes transferred in 5.828395 secs (184225983 bytes/sec) 184MB/sec! And this is synchronous writing, not random! So what is ZFS good for finally ? Synchronous writing or small random iops ? By the way, this is how the array is configured with 3ware: Unit UnitType Status %RCmpl %V/I/M Stripe Size(GB) Cache AVrfy ------------------------------------------------------------------------------ u0 RAID-10 OK - - 64K 7450.5 ON ON VPort Status Unit Size Type Phy Encl-Slot Model ------------------------------------------------------------------------------ p0 OK u0 931.51 GB SATA 0 - WDC WD1002FBYS-01A6 p1 OK u0 931.51 GB SATA 1 - WDC WD1002FBYS-01A6 p2 OK u0 931.51 GB SATA 2 - WDC WD1002FBYS-01A6 p3 OK u0 931.51 GB SATA 3 - WDC WD1002FBYS-01A6 p4 OK u0 931.51 GB SATA 4 - WDC WD1002FBYS-01A6 p5 OK u0 931.51 GB SATA 5 - WDC WD1002FBYS-01A6 p6 OK u0 931.51 GB SATA 6 - WDC WD1002FBYS-01A6 p7 OK u0 931.51 GB SATA 7 - WDC WD1002FBYS-01A6 p8 OK u0 931.51 GB SATA 8 - WDC WD1002FBYS-01A6 p9 OK u0 931.51 GB SATA 9 - WDC WD1002FBYS-01A6 p10 OK u0 931.51 GB SATA 10 - WDC WD1002FBYS-01A6 p11 OK u0 931.51 GB SATA 11 - WDC WD1002FBYS-01A6 p12 OK u0 931.51 GB SATA 12 - WDC WD1002FBYS-01A6 p13 OK u0 931.51 GB SATA 13 - WDC WD1002FBYS-01A6 p14 OK u0 931.51 GB SATA 14 - WDC WD1002FBYS-01A6 p15 OK u0 931.51 GB SATA 15 - WDC WD1002FBYS-01A6
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