From mboxrd@z Thu Jan 1 00:00:00 1970 From: "H. Peter Anvin" Subject: Re: what superblock to use Date: Tue, 21 Apr 2009 10:31:07 -0700 Message-ID: <49EE02DB.6020407@zytor.com> References: <49EC7B22.8070805@lfarkas.org> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: Mario 'BitKoenig' Holbe Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids Mario 'BitKoenig' Holbe wrote: > Farkas Levente wrote: >> 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. > > No, raid6 survives the simultaneous failure of two disks. > Raid5 survives the simultaneous failure of one disk only. Even with a > hot-spare, after this failure you have a time frame where the spare is > synching and your array has no redundancy left. Thus, nearly every other > disk failure (except a failure on the synching spare) within this time > frame kills your array. > It's worth noting that a failure mode that is getting increasingly frequently reported is the failure of a drive *during sync*. I suspect that the cause is that synchronization puts different stresses on the drives than normal operation. -hpa -- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf.