From mboxrd@z Thu Jan 1 00:00:00 1970 From: NeilBrown Subject: Re: possibly silly question (raid failover) Date: Wed, 2 Nov 2011 12:48:16 +1100 Message-ID: <20111102124816.33a55447@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> <20111102092526.50b410b1@notabene.brown> <20111102013756.GA10763@www5.open-std.org> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=PGP-SHA1; boundary="Sig_/7j9_m3px.lmW46dlZAza_Tp"; protocol="application/pgp-signature" Return-path: In-Reply-To: <20111102013756.GA10763@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_/7j9_m3px.lmW46dlZAza_Tp Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable On Wed, 2 Nov 2011 02:37:56 +0100 keld@keldix.com wrote: > On Wed, Nov 02, 2011 at 09:25:26AM +1100, NeilBrown wrote: > > On Tue, 1 Nov 2011 23:15:39 +0100 keld@keldix.com wrote: > >=20 > > > 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 ar= e=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 di= sks,=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 loose 2 disks out of 4. > >=20 > > With md/raid10 you can in some case lose 2 out of 4 disks and survive, = just > > like raid1+0. >=20 > OK, in which cases, and when is this not the case? >=20 > best regards > keld "just like raid1+0" NeilBrown --Sig_/7j9_m3px.lmW46dlZAza_Tp Content-Type: application/pgp-signature; name=signature.asc Content-Disposition: attachment; filename=signature.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.18 (GNU/Linux) iQIVAwUBTrChYDnsnt1WYoG5AQJY8hAAutudp/SCJAQr0cjIdb5T3ruKtmMShiOw L3ifw9mWqd046Ko/VbqehkjPAFH9Q//ESNwdKb36y7qU0xDfvIH4fmz2+jUnxwFZ KHWtznQHMJh+0PB5v+Pb3r7SZg1ByCxz88U7gRUAxQWODYoQx6JoP5+UTuAEKMEW 9Q+LD9PxpxFmyOBwaAZq+1ithWY3nMoyuUZXKlMbyUx6J+ztgzggCNRbOnCfzKUP RXlL6OH6jDVvS6OOJ0B3M2bJfw8at3Km3ayiV2pxVeD3q/a/V/GU8D9wSQ1crcFz QOG2x3fd54h8miWWkM0Cl/UifrKS3eGX4cd5JeM/V9Ysf6GJ2X+7a3BGpllURJmd QhLMitRCaR1hhxJXdDzdgdXcuqeqVE2EKqWWgLJOvpm4uDjzgjhwfAvLVikidR6w O4ZMVHJLCLwM1VMtQIgVlOD2zXUqQKgu2fQcC048G4rfbQ9WNoInvy7Tf6UtNaGA 2nsUggVBDDw2/YtYtUW6MNXFIc4AKk5PSwYovHerFawyPXcq/2cedBah9DFNLzre TEfOO7IFCHKkISYrPTpYZAFIK276cG6D6BWVSS1XVz7O/t4yknR9SUj3aaz7Q3dm l1cE1FNPhmUuCIz8hOquo5D+mESt5IjaemTgGE7ByTJa90fyfbFEinq3I3aVn5qN fSvjzOUW81k= =vF8u -----END PGP SIGNATURE----- --Sig_/7j9_m3px.lmW46dlZAza_Tp--