Date: Sat, 23 May 2009 09:26:45 -0400 From: Adam McDougall <mcdouga9@egr.msu.edu> To: Randy Bush <randy@psg.com> Cc: freebsd-fs <freebsd-fs@freebsd.org>, Artis Caune <artis.caune@gmail.com> Subject: Re: raidz2 a bit big Message-ID: <20090523132644.GN35763@egr.msu.edu> In-Reply-To: <m27i08km2j.wl%randy@psg.com> References: <m28wkon90c.wl%randy@psg.com> <9e20d71e0905230537ibcaf852g1dc32b6ffc3a681d@mail.gmail.com> <m27i08km2j.wl%randy@psg.com>
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On Sat, May 23, 2009 at 06:04:04AM -0700, Randy Bush wrote: >> NAME STATE READ WRITE CKSUM >> tank ONLINE 0 0 0 >> raidz2 ONLINE 0 0 0 >> da0s3 ONLINE 0 0 0 >> da1s3 ONLINE 0 0 0 >> da2s1 ONLINE 0 0 0 >> da3s1 ONLINE 0 0 0 >> da4s1 ONLINE 0 0 0 >> da5s1 ONLINE 0 0 0 >> da6s1 ONLINE 0 0 0 >> da7s1 ONLINE 0 0 0 >> da8s1 ONLINE 0 0 0 >> da9s1 ONLINE 0 0 0 >> da10s1 ONLINE 0 0 0 >> da11s1 ONLINE 0 0 0 > > Reads on such configurations are very slow. how are writes? > If one of your disk, for example, is capable of 100 IO per/sec, then: > with 12 disks in one raidz2 vdev you get only 100 IOPS > with 4 disks in raidz2 (total 3 raidz2 vdevs) you get 300 IOPS > with 2 disks in mirror (total 6 mirror vdevs) you can get 1200 IOPS ok. sounds nice. but then, don't i have six file systems and have to start playing lay-out design games? randy For an example: (btw the read speed is fantastic in a mirror and the write is notably faster than raidz, but if your I/O is all going to go through a gig nic, then it may not matter such as if you are just using it for a low concurrent user stash of large files) zpool create tank mirror aacd0s1d aacd1s1d mirror aacd2s1d aacd3s1d mirror aacd4s1d aacd5s1d mirror aacd6s1d aacd7s1d # zpool status pool: tank state: ONLINE scrub: none requested config: NAME STATE READ WRITE CKSUM tank ONLINE 0 0 0 mirror ONLINE 0 0 0 aacd0s1d ONLINE 0 0 0 aacd1s1d ONLINE 0 0 0 mirror ONLINE 0 0 0 aacd2s1d ONLINE 0 0 0 aacd3s1d ONLINE 0 0 0 mirror ONLINE 0 0 0 aacd4s1d ONLINE 0 0 0 aacd5s1d ONLINE 0 0 0 mirror ONLINE 0 0 0 aacd6s1d ONLINE 0 0 0 aacd7s1d ONLINE 0 0 0
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