From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bill Davidsen Subject: Re: Proposal: non-striping RAID4 Date: Wed, 14 Nov 2007 18:16:14 -0500 Message-ID: <473B81BE.8070309@tmr.com> References: <4737AC62.8000308@tmr.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: James Lee Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids James Lee wrote: > >From a quick search through this mailing list, it looks like I can > answer my own question regarding RAID1 --> RAID5 conversion. Instead > of creating a RAID1 array for the partitions on the two biggest > drives, it should just create a 2-drive RAID5 (which is identical, but > can be expanded as with any other RAID5 array). > > So it looks like this should work I guess. I believe what you want to create might be a three drive raid-5 with one failed drive. That way you can just add a drive when you want. mdadm -C -c32 -l5 -n3 -amd /dev/md7 /dev/loop[12] missing Then you can add another drive: mdadm --add /dev/md7 /dev/loop3 The output are at the end of this message. But in general think it would be really great to be able to have a format which would do raid-5 or raid-6 over all the available parts of multiple drives, and since there's some similar logic for raid-10 over a selection of drives it is clearly possible. But in terms of the benefit to be gained, unless it fails out of the code and someone feels the desire to do it, I can't see much joy to ever having such a thing. The feature I would really like to have is raid5e, distributed spare so head motion is spread over all drives. Don't have time to look at that one, either, but it really helps performance under load with small arrays. -- bill davidsen CTO TMR Associates, Inc Doing interesting things with small computers since 1979