Date: Mon, 13 Jul 2009 09:00:06 GMT From: "Steiner, Bernard" <Bernard.Steiner@lahmeyer.de> To: freebsd-geom@FreeBSD.org Subject: RE: kern/121481: [gmirror] data rot on disk with gmirror Message-ID: <200907130900.n6D906TE039950@freefall.freebsd.org>
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The following reply was made to PR kern/121481; it has been noted by GNATS. From: "Steiner, Bernard" <Bernard.Steiner@lahmeyer.de> To: "Dan Naumov" <dan.naumov@gmail.com>, <bug-followup@FreeBSD.org> Cc: Subject: RE: kern/121481: [gmirror] data rot on disk with gmirror Date: Mon, 13 Jul 2009 10:50:02 +0200 Dan, > RAID offers protection against very specific kinds of disk > failure and does not offer any kind of protection against bit > rot. I want to emphasize that this is not a FreeBSD issue, > but a RAID issue in general and you will run into exact same > limitations if you try raid on Linux or Windows or hardware I was asking for -w to be implemented by gmirror, and/or graid6 (double parity) be implemented (also with -w or even -w2 ;-) > raid from any hardware vendor. For another example of a fault > that RAID mirror will NOT protect you or even warn you > against, is your disk/raid controller going berserk and > writing garbage to the mirror or one of it's member disks. ACK. This is exactly why I want a check on the data read. > [checksumming utilities] Please explain how to do that on both sides of a gmirror. AFAIK, gmirror can be configured in the following ways: (1) always read from "primary" disk => cannot check secondary (2) round robin or load => read cannot be reliably reproduced Correct me if I am wrong, but this does not seem like a solution to my problem. > [ZFS / Solaris] I think I *like* ZFS (raidz2) and probably go with that. Solaris' future is uncertain in the light of SUN's future... I think maybe I'll wait a while till the warning is edited out of ZFS in FreeBSD and give it another shot. Bernard -- i.A. Dipl.-Inform. Bernard Steiner Netzwerk- und Systemadministrator Phone: +49 6101 55 1280, Fax: +49 6101 55 1623 Lahmeyer International GmbH Friedberger Strasse 173, 61118 Bad Vilbel, Deutschland/Germany Geschaeftsfuehrer/Managing Directors: Dr. Henning Nothdurft (Vorsitzender/President), Burkhard Neumann Firmensitz/Registered office: Bad Vilbel Registergericht/Registry court: Frankfurt am Main HRB 80852 Internet: http://www.lahmeyer.de/ Disclaimer: http://www.lahmeyer.de/disclaimer/
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