From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bill Davidsen Subject: Re: First RAID Setup Date: Thu, 22 Dec 2005 09:00:46 -0500 Message-ID: <43AAB18E.70009@tmr.com> References: <0481A62A3E95A044AC20A1A45899645C06B02F4A@glc-mail-1.tessco.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <0481A62A3E95A044AC20A1A45899645C06B02F4A@glc-mail-1.tessco.com> Sender: linux-raid-owner@vger.kernel.org To: "Callahan, Tom" Cc: 'Andargor The Wise' , linux-raid@vger.kernel.org List-Id: linux-raid.ids Callahan, Tom wrote: >You "should" have a designated spare for RAID-5. > >Not sure why you have 3 disks for each RAID1, RAID1 is mirror, and unless >the third drive is a spare, it is not needed. > >Thanks, >Tom Callahan > > Why would you have a hot spare? In RAID-1 if one drive failed you would copy the full set of data to the "spare" so you know what to copy, another mirror can help your read performance under heavy load. You get the same protection as a hot spare, it's online if you need it, it covers the case where two drives fail... what's not to like? ;-) If a third drive is justified, I see no reason to keep it as a spare rather than a live mirror in RAID-1. -- bill davidsen CTO TMR Associates, Inc Doing interesting things with small computers since 1979