From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: Some very basic questions Date: Wed, 22 Oct 2008 17:39:04 +0200 Message-ID: <48FF4918.6070600@redhat.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> <48FF3CB9.6070404@redhat.com> <48FF3EB8.6050306@redhat.com> <48FF4082.407@redhat.com> <48FF4302.5030204@redhat.com> <48FF45EE.7010001@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Cc: Chris Mason , Stephan von Krawczynski , Christoph Hellwig , jim owens , linux-btrfs@vger.kernel.org To: Ric Wheeler Return-path: In-Reply-To: <48FF45EE.7010001@redhat.com> List-ID: Ric Wheeler wrote: > I think that the btrfs plan is still to push more complicated RAID > schemes off to MD (RAID6, etc) so this is an issue even with a JBOD. > It will be interesting to map out the possible ways to use built in > mirroring, etc vs the external RAID and actually measure the utilized > capacity and performance (online & during rebuilds). That's leaving a lot of performance and features on the table, IMO. We definitely want to have metadata and small files using mirroring (perhaps even three copies for some metadata). Use RAID[56] for large files. Perhaps even start files at RAID1, and have the scrubber convert them to RAID[56] when it notices they are only ever read. Keep temporary or unimportant files at RAID0. Play games with asymmetric setups (small fast disks + large slow disks). etc etc etc. Delegating things to MD throws out a lot of metadata so these things become impossible. -- error compiling committee.c: too many arguments to function