From mboxrd@z Thu Jan 1 00:00:00 1970 From: Miles Fidelman Subject: Re: possibly silly question (raid failover) Date: Tue, 01 Nov 2011 18:38:38 -0400 Message-ID: <4EB074EE.10709@meetinghouse.net> 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> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20111102092526.50b410b1@notabene.brown> Sender: linux-raid-owner@vger.kernel.org Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids NeilBrown wrote: > 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 >>>> right that md RAID10 offers more than RAID1 (or traditional RAID0 over >>>> RAID1 sets) - but it is a convenience and performance benefit, not a >>>> redundancy benefit. In particular, it lets you build RAID10 from any >>>> number of disks, not just two. And it lets you stripe over all disks, >>>> improving performance for some loads (though not /all/ loads - if you >>>> have lots of concurrent small reads, you may be faster using plain >>>> RAID1). >> 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. > it occurs to me that it's a real bummer that all the md documentation, that was on raid.wiki.kernel.org, has been inaccessible since the kernel.org hack a couple of months ago -- anybody know if that's going to be back soon, or if that documentation lives somewhere else as well? -- In theory, there is no difference between theory and practice. In practice, there is. .... Yogi Berra