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 20:29:39 +0200 Message-ID: <20110506182939.GA23860@www2.open-std.org> References: <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> <20110506152405.GB22964@www2.open-std.org> 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: Sender: linux-raid-owner@vger.kernel.org To: Roberto Spadim Cc: Keld =?iso-8859-1?Q?J=F8rn?= Simonsen , Miles Fidelman , linux-raid@vger.kernel.org List-Id: linux-raid.ids On Fri, May 06, 2011 at 12:34:36PM -0300, Roberto Spadim wrote: > hum, i asked this question one time, the point is: > raid1 code is very easy > raid10 code is more complex >=20 > easy =3D faster, less memory, less cpu > complex =3D faster?, more memory? more cpu? I think more complex -> more intelligent, more features. I think it is actually amazing what raid10 can do. Is raid 1 in other systems really limited to say 2 disks - mirrored? Then linux raid10 is much more intelligent.=20 >=20 > check others raid system (freebsd, netbsd) and check how they do... Yes, and also HW raid. If Linux made raid10,far the default for RAID1, then I think Linux would compare very well with other operating systems and HW raid. Best regards keld ---- > 2011/5/6 Keld J=F8rn Simonsen : > > 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 t= o > >> >>RAID1+0 - i.e., a stripe of two normal RAID1 pairs. > >> >> > >> > >> I don't that's exactly right. =A0At least as I understand it: > >> > >> - RAID1+0 (and RAID0+1) nests things - you start with two sets of = RAID1 > >> mirrors, then stripe across them (or vice versa) - it's a nested s= et of > >> steps > >> > >> - md RAID10 provides both mirroring and striping, but it's a more > >> integrated function - (from the man page) "RAID10 provides a combi= nation > >> of RAID1 and RAID0, and sometimes known as RAID1+0. Every databloc= k is > >> duplicated some number of times, and the resulting collection of > >> datablocks are distributed over multiple drives." - but there isn'= t an > >> inherent nesting in the process (i.e., no two disks are copies of = each > >> 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= =2E > > 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-rai= d" in > > the body of a message to majordomo@vger.kernel.org > > More majordomo info at =A0http://vger.kernel.org/majordomo-info.htm= l > > >=20 >=20 >=20 > --=20 > Roberto Spadim > Spadim Technology / SPAEmpresarial -- 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