From mboxrd@z Thu Jan 1 00:00:00 1970 From: NeilBrown Subject: Re: possibly silly question (raid failover) Date: Wed, 2 Nov 2011 09:25:26 +1100 Message-ID: <20111102092526.50b410b1@notabene.brown> References: <4EAF3F78.5060900@meetinghouse.net> <4EAFEE95.6070608@meetinghouse.net> <4EAFF636.6060904@anonymous.org.uk> <4EB052E6.4050400@meetinghouse.net> <20111101221539.GA1319@www5.open-std.org> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=PGP-SHA1; boundary="Sig_/ik60z2cWbie0QRDJddUgueO"; protocol="application/pgp-signature" Return-path: In-Reply-To: <20111101221539.GA1319@www5.open-std.org> Sender: linux-raid-owner@vger.kernel.org To: keld@keldix.com Cc: Miles Fidelman , linux-raid@vger.kernel.org List-Id: linux-raid.ids --Sig_/ik60z2cWbie0QRDJddUgueO Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable On Tue, 1 Nov 2011 23:15:39 +0100 keld@keldix.com wrote: > On Tue, Nov 01, 2011 at 04:13:26PM -0400, Miles Fidelman wrote: > > David Brown wrote: > > > > > >No, md RAID10 does /not/ offer more redundancy than RAID1. You are=20 > > >right that md RAID10 offers more than RAID1 (or traditional RAID0 over= =20 > > >RAID1 sets) - but it is a convenience and performance benefit, not a=20 > > >redundancy benefit. In particular, it lets you build RAID10 from any= =20 > > >number of disks, not just two. And it lets you stripe over all disks,= =20 > > >improving performance for some loads (though not /all/ loads - if you= =20 > > >have lots of concurrent small reads, you may be faster using plain=20 > > >RAID1). >=20 > In fact raid10 mas a bit less redundancy than raid1+0. > It is as far as I know built as raid0+1 with a disk layout > where you can only loose eg 1 out of 4 disks, while raid1+0 > in some cases can lose 2 disks out of 4. With md/raid10 you can in some case lose 2 out of 4 disks and survive, just like raid1+0. NeilBrown >=20 > Also for lots of concurrent small reads raid10 can in some cases be somew= hat > faster than raid1, and AFAIK never slower than raid1.=20 >=20 > Best regards > keld > -- > To unsubscribe from this list: send the line "unsubscribe linux-raid" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html --Sig_/ik60z2cWbie0QRDJddUgueO Content-Type: application/pgp-signature; name=signature.asc Content-Disposition: attachment; filename=signature.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.18 (GNU/Linux) iQIVAwUBTrBx4Dnsnt1WYoG5AQLwbA/+PLtTnyRZ/KErjZSVRWf5Ub1fUeB35fio yOGmgrBFj2ZO2YuDmFW2xyQl2yyPxlui3WEAQN2saSqIhG4Cg7f66qON3FT8eqGS XCJ/zkC/7cY40+fqyJY+b1ut0IoaB3kj2gzAJZOrRBoqURx7JCkcYaYuTRPFMQOh fFvX6eBG59eXH251+lTeQEvb/Wuvbc5XB3hmyeNQjvJmxAeDYN27gRARwBrrsKN3 jbEiGkyjuHz4LFIrr3rvoFcwsu9ik+iW1BCXaSJs9hbCreS7MS/q0U/0JMuNU84N t6G4T5fvOgViwgwFjoq0ajrcYFj1CgupoQ3ARKkPpwc5i8vQGZeEZlgIuJBXlhb5 UOC8F5smjYjFpbwTGVfSd367tMbggGWaFkLlqOsJFp5DMdhyq9Yie/dEdE4g9V/l tSXEVhaF3cTOxPa/mb+8EsBPaA90WZAcwAlnstKcMLOXE9bcpGJ9M+DaCyCqqrBX lFnMxjbfsq8Mh41x/EhcBj0+tXJlK06Rdpg7f+TWEJSmSPwVQZ/kEGRU/xxVoxH3 LWQPyBPVfYnakcbNy4YuulqaNbO/gKErE+/myAohAxtlyxLdLKCtxR2QM1aDwNp7 8BgTcAOW+XA3TJB4LrSYEQJohLDck5z9fJ4rcRHwle+nm9lO/Zrg75zVnl2GtO55 dsJ5tlVyC2g= =Rv38 -----END PGP SIGNATURE----- --Sig_/ik60z2cWbie0QRDJddUgueO--