Date: Wed, 24 Mar 2010 21:23:54 +0000 From: krad <kraduk@googlemail.com> To: Matthew Seaman <m.seaman@infracaninophile.co.uk> Cc: John <comp.john@googlemail.com>, freebsd-questions@freebsd.org Subject: Re: simple zfs query Message-ID: <d36406631003241423x4fade0dfra3f45f2f4784648c@mail.gmail.com> In-Reply-To: <4BA9F87E.7050205@infracaninophile.co.uk> References: <20100324103151.GA2598@potato> <4BA9F87E.7050205@infracaninophile.co.uk>
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On 24 March 2010 11:33, Matthew Seaman <m.seaman@infracaninophile.co.uk>wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > On 24/03/2010 10:31:51, John wrote: > > With ZFS and 3x 2Tb SATA disks, what percentage of theoretical diskspace > > would I realise? I'm hoping at least 5Tb would be usable? > > That depends on how you configure your zpool. The choices are: > > disk -- just uses the disk directly as a vdev. Means you can use 100% > of the space, but you have absolutely no resilience > > mirror -- for which you'ld need an even number of disks and you get 50% > of the raw as usable space. Can survive at least one disk > failure, and possibly up to as many as half of the disks > failing. > > raidz -- single parity (equivalent to RAID5). For N disks, 1 disk > worth is used for parity data, leaving N - 1 disks' worth as > the actual capacity. So you'ld get 66% of raw in your case. > Can survive failure of any one disk. > > raidz2 -- double parity (equivalent to RAID6). For N disks, 2 disks > worth are used for parity data, leaving N - 2 disks worth as > actual capacity. Or 33% of raw in your case. Can survive > failure of any two disks. > > Note that 3 drives is the minimum for either of the raidz types, and > won't give you the best performance. See zpool(1M) for details. > > Cheers, > > Matthew > > - -- > Dr Matthew J Seaman MA, D.Phil. 7 Priory Courtyard > Flat 3 > PGP: http://www.infracaninophile.co.uk/pgpkey Ramsgate > Kent, CT11 9PW > -----BEGIN PGP SIGNATURE----- > Version: GnuPG/MacGPG2 v2.0.14 (Darwin) > Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ > > iEYEARECAAYFAkup+H4ACgkQ8Mjk52CukIx8HQCfcGTI3wh3QsxNmDS1nPkbw8WU > cWIAoJO8rys1R7SfasVkse2htfqOqVrF > =AWpE > -----END PGP SIGNATURE----- > _______________________________________________ > freebsd-questions@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-questions > To unsubscribe, send any mail to " > freebsd-questions-unsubscribe@freebsd.org" > If you want 100% of the drives you could have a pool per drive. Its not as nice as one big pool, but its less risky than one big raid0
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