From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sebastian Riemer Subject: Re: Raid 0+1 Date: Fri, 30 Nov 2012 15:40:30 +0100 Message-ID: <50B8C55E.1050902@profitbricks.com> References: <50B8C26C.7000807@profitbricks.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <50B8C26C.7000807@profitbricks.com> Sender: linux-raid-owner@vger.kernel.org To: Oguz Yilmaz Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids On 30.11.2012 15:27, Sebastian Riemer wrote: > On 30.11.2012 14:25, Oguz Yilmaz wrote: >> What is the suggested way for making Raid 0+1 (not 1+0)? >> Is it possible to make it without LVM? > > Yes, it is possible but it only makes sense if you want to mirror to > another server as most people know that the alternative DRBD is too slow > for serious storage requirements. > > Create the RAID-0 first, then take your RAID-0 device and e.g. an iSCSI > device from another storage server with the same setup and create a > RAID-1 over them. Then, you've got your stacked MD layers. > > With the flag write-mostly you can even tell the read balancing that the > remote device is slower than the local one. > I've forgotten to mention: You need a kernel >= 3.4.2 for this. Earlier kernels don't support bvec merging and therefore every IO is a slow 4 KiB IO in that RAID 0+1 setup. Btw.: LVM also supports striping but letting LVM do striping is only useful if you want to build RAID 1+0. The speed is the same as "RAID 1+0 + LVM". Only that raid10 driver doesn't scale good for >= 24 HDDs.