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 11:41:02 +0200 Message-ID: <20110506094102.GC22245@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> 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: <4DC3BDD9.1060300@abpni.co.uk> Sender: linux-raid-owner@vger.kernel.org To: Jonathan Tripathy Cc: Keld =?iso-8859-1?Q?J=F8rn?= Simonsen , Roman Mamedov , linux-raid@vger.kernel.org List-Id: linux-raid.ids On Fri, May 06, 2011 at 10:22:33AM +0100, Jonathan Tripathy wrote: >=20 > 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-o= ffset > >>>layout is an implementation of a SNIA RAID specification. The RAID= 10-near > >>>layout is an implementation of a simple RAID layout. And the RAID1= 0-far > >>>layout is just another layout far a mirrored RAID. So all these t= ypes > >>>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, an= d > >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 roughl= y=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 disk= s),=20 > but with each disk having a mirror (which brings the total up to 4 dr= ives). >=20 > Additionally, a RAID1 disk (at least using MD) can be accessed just l= ike=20 > a normal disk (good for recovery etc.) however a single disk out of a= =20 > RAID10 array is next to useless. I think you are demonstrating some of my points about general knowledge quite nicely. Don't worry, you are not alone. best regards 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