Date: Mon, 01 Jun 2009 13:50:12 +0100 From: Tom Evans <tevans.uk@googlemail.com> To: krad <kraduk@googlemail.com> Cc: freebsd-hackers@freebsd.org, xorquewasp@googlemail.com Subject: RE: Request for opinions - gvinum or ccd? Message-ID: <1243860612.9871.68.camel@strangepork.london.mintel.ad> In-Reply-To: <3346D963EE2E4D28AE89CB71C2F92939@uk.tiscali.intl> References: <20090530175239.GA25604@logik.internal.network> <20090530144354.2255f722@bhuda.mired.org> <20090530191840.GA68514@logik.internal.network> <20090530162744.5d77e9d1@bhuda.mired.org> <A5BB2D2B836A4438B1B7BD8420FCC6A3@uk.tiscali.intl> <20090531201445.GA82420@logik.internal.network> <alpine.BSF.2.00.0905312355240.26545@wojtek.tensor.gdynia.pl> <0229B3BF1BE94C82AA11FD06CBE0BDEF@uk.tiscali.intl> <20090531235943.GA77374@logik.internal.network> <3346D963EE2E4D28AE89CB71C2F92939@uk.tiscali.intl>
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On Mon, 2009-06-01 at 09:32 +0100, krad wrote: > Zfs has been designed for highly scalable redundant disk pools therefore > using it on a single drive kind of goes against it ethos. Remember a lot of > the blurb in the man page was written by sun and therefore is written with > corporates in mind, therefore the cost with of the data vs an extra drive > being so large why wouldn't you make it redundant. > > Having said that sata drives are cheap these days so you would have to be on > the tightest of budgets not to do a mirror. > > Having said all this we quite often us zfs on a single drive, well sort of. > The sun clusters have external storage for the shared file systems. These > are usually a bunch of drives, raid 5, 10 or whatever. Then export a single > lun, which is presented to the various nodes. There is a zpool created on > this LUN. So to all intents and purposes zfs thinks its on a single drive > (the redundancy provided by the external array). This is common practice and > we see no issues with it. By doing this surely you lose a lot of the self healing that ZFS offers? For instance, if the underlying vdev is just a raid5, then a disk failure combined with an undetected checksum error on a different disk would lead you to lose all your data. Or am I missing something? (PS, top posting is bad) Tom
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