From mboxrd@z Thu Jan 1 00:00:00 1970 From: keld@keldix.com Subject: Re: possibly silly question (raid failover) Date: Tue, 1 Nov 2011 23:15:39 +0100 Message-ID: <20111101221539.GA1319@www5.open-std.org> References: <4EAF3F78.5060900@meetinghouse.net> <4EAFEE95.6070608@meetinghouse.net> <4EAFF636.6060904@anonymous.org.uk> <4EB052E6.4050400@meetinghouse.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <4EB052E6.4050400@meetinghouse.net> Sender: linux-raid-owner@vger.kernel.org To: Miles Fidelman Cc: no@open-std.org, To-header@open-std.org, on@open-std.org, "input <"@open-std.org, linux-raid@vger.kernel.org List-Id: linux-raid.ids 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. Also for lots of concurrent small reads raid10 can in some cases be somewhat faster than raid1, and AFAIK never slower than raid1. Best regards keld