From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chris Mason Subject: Re: Some very basic questions Date: Wed, 22 Oct 2008 10:36:55 -0400 Message-ID: <1224686215.6448.49.camel@think.oraclecorp.com> References: <20081021132322.271ad728.skraw@ithnet.com> <48FDD710.5050702@hp.com> <20081021190136.89b2c6af.skraw@ithnet.com> <20081021171513.GA8799@infradead.org> <48FE11F9.7040700@gmail.com> <20081022142759.ac33a16c.skraw@ithnet.com> <1224681345.6448.4.camel@think.oraclecorp.com> <48FF2A5B.80108@redhat.com> <48FF396B.1020700@redhat.com> Mime-Version: 1.0 Content-Type: text/plain Cc: Ric Wheeler , Stephan von Krawczynski , Christoph Hellwig , jim owens , linux-btrfs@vger.kernel.org To: Avi Kivity Return-path: In-Reply-To: <48FF396B.1020700@redhat.com> List-ID: On Wed, 2008-10-22 at 16:32 +0200, Avi Kivity wrote: > Ric Wheeler wrote: > > One key is not to replace the drives too early - you often can recover > > significant amounts of data from a drive that is on its last legs. > > This can be useful even in RAID rebuilds since with today's enormous > > drive capacities, you might hit a latent error during the rebuild on > > one of the presumed healthy drives. > > > > Of course, if you don't have a spare drive in your configuration, this > > is not practical... > > Why would you have a spare drive? That's a wasted spindle. > > You want to have spare capacity, enough for one or two (or fifteen) > drives' worth of data. When a drive goes bad, you rebuild into the > spare capacity you have. > You want spare capacity that does not degrade your raid levels if you move the data onto it. In some configs, this will be a hot spare, in others it'll just be free space. -chris