Date: Fri, 1 Jan 2010 17:05:25 -0600 (CST) From: Bob Friesenhahn <bfriesen@simple.dallas.tx.us> To: "ticso@cicely.de" <ticso@cicely.de> Cc: "freebsd-fs@freebsd.org" <freebsd-fs@freebsd.org> Subject: Re: ZFS RaidZ2 with 24 drives? Message-ID: <alpine.GSO.2.01.1001011656320.1586@freddy.simplesystems.org> In-Reply-To: <20100101223907.GX43739@cicely7.cicely.de> References: <55389.88569.qm@web112405.mail.gq1.yahoo.com> <20100101204752.GW43739@cicely7.cicely.de> <alpine.GSO.2.01.1001011538130.1586@freddy.simplesystems.org> <20100101223907.GX43739@cicely7.cicely.de>
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On Fri, 1 Jan 2010, Bernd Walter wrote: > > There are many possible reasons why this won't happen. > One of them is a simple write failure, which can't be reported back > to the filesystem, because not even a cache flush fails. For most RAID systems (and for ZFS) it is best if write failures are tossed because there should be a redundant copy somewhere else. Write failures usually indicate a completely failed disk since modern disks include their own bad-block management. The most important thing for ZFS is that transaction group writes are written in order, as demarcated by transaction group cache sync requests. Otherwise you get a scrambled pool which may require an expert human to untangle. > The main problem I see is that such controllers won't tell about > their strategy, so you are left in the dark. That is unfortunate. Bob -- Bob Friesenhahn bfriesen@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/
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