Date: Mon, 1 Jun 2009 09:42:24 +0100 From: krad <kraduk@googlemail.com> To: "'Wojciech Puchar'" <wojtek@wojtek.tensor.gdynia.pl>, "'Mike Meyer'" <mwm-keyword-freebsdhackers2.e313df@mired.org> Cc: freebsd-hackers@freebsd.org, xorquewasp@googlemail.com Subject: RE: Request for opinions - gvinum or ccd? Message-ID: <442651299CA2445991E65F64AF9E65D7@uk.tiscali.intl> In-Reply-To: <alpine.BSF.2.00.0906010224050.27329@wojtek.tensor.gdynia.pl> 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><20090531201408.45dd4334@bhuda.mired.org> <alpine.BSF.2.00.0906010224050.27329@wojtek.tensor.gdynia.pl>
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You shouldn't need to alter the copies attribute to recover from disk failures as the normal raid should take care of that. What the copies is useful for is when you get undetected write errors on the drive due to crc collisions or the drive simply being rubbish Zfs will intelligently assign the copies across multiple drives if possible, so if you had 3 vdevs and copies set to three, One copy should end up on each vdev. Note this isn't the same as mirroring, as each vdev could be a raidz2 group. With copies=1 you would get a 3rd of the file on each. With copies 3 you would get a full version of each. This is obviously very costly on drive space though. It is tunable per file system though so you don't have to enable it for the whole pool just the bits you want. -----Original Message----- From: owner-freebsd-hackers@freebsd.org [mailto:owner-freebsd-hackers@freebsd.org] On Behalf Of Wojciech Puchar Sent: 01 June 2009 01:26 To: Mike Meyer Cc: freebsd-hackers@freebsd.org; xorquewasp@googlemail.com Subject: Re: Request for opinions - gvinum or ccd? > Disks, unlike software, sometimes fail. Using redundancy can help modern SATA drives fail VERY often. about 30% of drives i bought recently failed in less than a year. > both checksum on and copies > 1 on, and the latter isn't the > default. It's probably better to let zpool provide the redundancy via > a mirror or raid configuration than to let zfs do it anyway. ZFS copies are far from what i consider useful. for example you set copies=2. You write a file, and get 2 copies. Then one disk with one copy fails, then you put another, do resilver but ZFS DOES NOT rebuild second copy. You need to write a program that will just rewrite all files to make this. _______________________________________________ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "freebsd-hackers-unsubscribe@freebsd.org"
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