Date: Fri, 22 May 2009 16:15:13 -0500 From: Brooks Davis <brooks@freebsd.org> To: Randy Bush <randy@psg.com> Cc: freebsd-fs <freebsd-fs@freebsd.org> Subject: Re: raidz2 a bit big Message-ID: <20090522211513.GB2160@lor.one-eyed-alien.net> In-Reply-To: <m28wkon90c.wl%randy@psg.com> References: <m28wkon90c.wl%randy@psg.com>
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[-- Attachment #1 --] On Fri, May 22, 2009 at 02:05:39PM -0700, Randy Bush wrote: > a dozen 2tb drives in a raidz2 > > dfw1.psg.com:/root# zpool status > pool: tank > state: ONLINE > scrub: none requested > config: > > 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 > > errors: No known data errors > > i expected to get 10T effective because of the raidz2, but got 20T > ^ > dfw1.psg.com:/root# df -H > Filesystem Size Used Avail Capacity Mounted on > /dev/da0s1a 17G 3.8G 12G 25% / > devfs 1.0k 1.0k 0B 100% /dev > /dev/md0 130M 90k 119M 0% /tmp > tank 19T 0B 19T 0% /tank > tank/usr 19T 0B 19T 0% /tank/usr > tank/usr/home 19T 0B 19T 0% /tank/usr/home > tank/var 19T 0B 19T 0% /tank/var > tank/var/spool 19T 0B 19T 0% /tank/var/spool > tank/data 19T 0B 19T 0% /tank/data > > clue bat? raidz2 is RAID6ish in that two disks of a raid group go to parity to allow you to survive double faults. Thus your expected size is: (12-2)*2TB = 20TB. -- Brooks [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (FreeBSD) iD8DBQFKFxXgXY6L6fI4GtQRAuJiAKCeRp31X+4k+uttIL2T8Z+EIcpn7QCdGCPi NDyhemHtfwYHfASZ2d/Iw7s= =PUtN -----END PGP SIGNATURE-----
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