From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gavin McCullagh Subject: Re: LINEAR RAID, little help Date: Sat, 7 Apr 2007 21:34:35 +0100 Message-ID: <20070407203435.GA32499@gmail.com> References: <46177DD8.9080707@pcfusion.co.uk> <20070407173352.GA23645@gmail.com> <4617E5E2.2090609@pcfusion.co.uk> Reply-To: Gavin McCullagh Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <4617E5E2.2090609@pcfusion.co.uk> Sender: linux-raid-owner@vger.kernel.org To: Rich Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids Hi, On Sat, 07 Apr 2007, Rich wrote: > Er, I went with Linear as reading around people seemed to recommend this > for odd sized drives (my old drives are 80's, 120 and 320's) also a read > somewhere that data on the other drives is more recoverable that most of > the other RAID's. You just want to make a large filesystem out of odd sized disks. I guess that's fair enough. The only reservation I'd have is that with N disks your likelihood of failure is multiplied by N as any disk failure takes the array down. Personally, I'd be more inclined to try and put a separate filesystem on each disk and use symlinks to pull them together into one tree. But now I know why linear raid can be more useful than raid-0, thanks. > Well it contains stuff like TV and films a lot of which my friends have, > so loosing it is not that big of a deal just inconvenient. As I said > before I read linear was a better choice for odd sized drives and had > better data recovery that the other RAID's I guess you're using it similarly to LVM then. http://en.wikipedia.org/wiki/Logical_Volume_Manager_(Linux) http://tldp.org/HOWTO/LVM-HOWTO/ It sounds reasonable that recovery would be more feasible than RAID-0 but neither would be nice to have to do. RAID1, 5, etc. would be less likely to require recovery as they have redundancy so a single disk failure shouldn't take down the array at all. > I'm sure I read somewhere on the mdadm page in one of the posts about > adding support for linear growing, and that was dated 2004 so it might > be in there? Just wasn't to sure how to do it... This looks like your page. http://cgi.cse.unsw.edu.au/~neilb/SoftRaid and the mdadm changelog has it: Changes Prior to 1.7.0 release - Support "--grow --add" to add a device to a linear array, if the kernel supports it. Not documented yet. I've only grown raid5 arrays myself. I imagine you must do --add to add the extra disk partition to the array and then do "mdadm --grow --size=max", same as with raid5. Gavin