From mboxrd@z Thu Jan 1 00:00:00 1970 From: Keld =?iso-8859-1?Q?J=F8rn?= Simonsen Subject: Re: wish for Linux MD mirrored raid types Date: Fri, 6 May 2011 17:24:06 +0200 Message-ID: <20110506152405.GB22964@www2.open-std.org> References: <20110506071752.GA22063@www2.open-std.org> <20110506133159.30c66519@natsu> <20110506090345.GA22245@www2.open-std.org> <4DC3BDD9.1060300@abpni.co.uk> <20110506094102.GC22245@www2.open-std.org> <20110506155059.6f82cbeb@natsu> <4DC3C804.6080200@abpni.co.uk> <20110506132739.GA22689@www2.open-std.org> <4DC3FF4C.5090502@meetinghouse.net> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Content-Disposition: inline In-Reply-To: <4DC3FF4C.5090502@meetinghouse.net> Sender: linux-raid-owner@vger.kernel.org To: Miles Fidelman Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids On Fri, May 06, 2011 at 10:01:48AM -0400, Miles Fidelman wrote: > Keld J=F8rn Simonsen wrote: > >>As you say, RAID10,near on four disks is pretty much identical to > >>RAID1+0 - i.e., a stripe of two normal RAID1 pairs. > >> =20 >=20 > I don't that's exactly right. At least as I understand it: >=20 > - RAID1+0 (and RAID0+1) nests things - you start with two sets of RAI= D1=20 > mirrors, then stripe across them (or vice versa) - it's a nested set = of=20 > steps >=20 > - md RAID10 provides both mirroring and striping, but it's a more=20 > integrated function - (from the man page) "RAID10 provides a combinat= ion=20 > of RAID1 and RAID0, and sometimes known as RAID1+0. Every datablock i= s=20 > duplicated some number of times, and the resulting collection of=20 > datablocks are distributed over multiple drives." - but there isn't a= n=20 > inherent nesting in the process (i.e., no two disks are copies of eac= h=20 > other, and md RAID10 will work over odd numbers of drives) Yes, you are right, RAID1+0 is nested, while Linux MD raid10 is not. But the data layout of Linux MD RAID1+0 and Linux MD RAID10,near is almost identical. keld -- To unsubscribe from this list: send the line "unsubscribe linux-raid" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html