Date: Tue, 01 Sep 2009 16:56:16 +0100 From: Pete French <petefrench@ticketswitch.com> To: fjwcash@gmail.com, freebsd-stable@freebsd.org Subject: Re: zfs on gmirror slice Message-ID: <E1MiViS-0004N3-U2@dilbert.ticketswitch.com> In-Reply-To: <b269bc570909010832s44cd4eb2ib612db6fabc3bf2d@mail.gmail.com>
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> ZFS includes support for RAID0 (stripe), RAID1 (mirroring), RAID5 and RAID6 > (raidz1/raidz2), and (soon in OpenSolaris) RAID7 (raidz3). Why would you > want to build a pool out of devices that are already RAID'd together? Because gmirror type RAIDing is more appropriate for your application than ZFS RAID ? I am not the original poster, but I can easily see why one would want to do do this. For example making a gmirror of a local drive and a remote drive - you can ask gmirror to prefer reads on the local disc, but there isn't a way to specify that in ZFS that I know of. Also gmirror on top of ggate behaves nicely if the remote drive fails. ZFS does not behave nicely at all - or it didn't when I ran tests. I havent tried on the latest version I admit. But ZFS as a filesystem still has many significant advantages, so runnng it on top of gmirror is actually a worthwhile thing to do. -pete.
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