From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bill Davidsen Subject: Re: what superblock to use Date: Tue, 21 Apr 2009 10:20:17 -0400 Message-ID: <49EDD621.5090804@tmr.com> References: <49EC7B22.8070805@lfarkas.org> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <49EC7B22.8070805@lfarkas.org> Sender: linux-raid-owner@vger.kernel.org To: Farkas Levente Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids Farkas Levente wrote: > hi, > what's the current recommended superblock to use for a newly created > raid5-6 array with 6 pieces of 1tb disk? by default mdamd use 0.90. is > it worth to change it to any 1.x format? > anyway is there any advantage of a raid6 over raid5+1spare disk? afaik > raid5 will be faster and use less cpu and both case 2 disk can failed. > thanks in advance. > > Let me be Devil's Advocate. The advantage of raid6 is that it will survive the failure of two drives at the same time, while a spare must be rebuilt (a good argument for fast rebuild and let response go to blazes). The advantage of raid5+S is that with a failure of a single drive you run your io in recovery mode, and it is slow, while after rebuild on the spare raid5+S is as fast as ever. I have been trying some things with raid5e, and as soon as I find a good primer on using events to kick the recovery off I will be able to report some sucess with this. My POC uses a script, and works fine if I poll to detect the disk failure. -- bill davidsen CTO TMR Associates, Inc "You are disgraced professional losers. And by the way, give us our money back." - Representative Earl Pomeroy, Democrat of North Dakota on the A.I.G. executives who were paid bonuses after a federal bailout.