From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jonathan Tripathy Subject: Re: wish for Linux MD mirrored raid types Date: Fri, 06 May 2011 10:22:33 +0100 Message-ID: <4DC3BDD9.1060300@abpni.co.uk> References: <20110506071752.GA22063@www2.open-std.org> <20110506133159.30c66519@natsu> <20110506090345.GA22245@www2.open-std.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <20110506090345.GA22245@www2.open-std.org> Sender: linux-raid-owner@vger.kernel.org To: =?ISO-8859-1?Q?Keld_J=F8rn_Simonsen?= Cc: Roman Mamedov , linux-raid@vger.kernel.org List-Id: linux-raid.ids On 06/05/2011 10:03, Keld J=F8rn Simonsen wrote: > On Fri, May 06, 2011 at 01:31:59PM +0600, Roman Mamedov wrote: > =20 >> On Fri, 6 May 2011 09:17:52 +0200 >> Keld J=F8rn Simonsen wrote: >> >> =20 >>> I would like linux MD raid10 functionality to be part of the Linux = MD >>> RAID1 module, and be called raid1. This is in accordance with the >>> use of the RAID1 term as standadized by SNIA. In fact the RAID10-of= fset >>> layout is an implementation of a SNIA RAID specification. The RAID1= 0-near >>> layout is an implementation of a simple RAID layout. And the RAID10= -far >>> layout is just another layout far a mirrored RAID. So all these ty= pes >>> could just be defined as different RAID1 layouts. >>> =20 >> RAID1 is RAID1, RAID10 is RAID10. >> RAID1 on 4 drives is very different from RAID10 on 4 drives. >> Don't add confusion by trying to rename RAID10 to RAID1. >> =20 > How are they different? > Say what is the difference between a Linux MD RAID1 with 4 disks, and > the default Linux MD RAID10 with 4 disks? (in the near layout)? > > =20 RAID1 is traditionally a mirror only setup (ok, some RAID=20 implementations may do some load-balancing of some sort). So a RAID1=20 with 4 disks is one data set copied onto 4 disks. Bandwidth is roughly=20 the same as a single disk (ignoring any load balancing). RAID10 is mirror and stripe. A RAID10 with 4 disks is similar to a 2=20 disk RAID0 (double bandwidth with data split in half across both disks)= ,=20 but with each disk having a mirror (which brings the total up to 4 driv= es). Additionally, a RAID1 disk (at least using MD) can be accessed just lik= e=20 a normal disk (good for recovery etc.) however a single disk out of a=20 RAID10 array is next to useless. -- 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