From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stan Hoeppner Subject: Re: linear raid, is partial recovery possible? Date: Mon, 28 Nov 2011 16:00:57 -0600 Message-ID: <4ED40499.3060903@hardwarefreak.com> References: Reply-To: stan@hardwarefreak.com Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: wilsonjonathan Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids On 11/28/2011 2:06 PM, wilsonjonathan wrote: > Or perhaps it is dependent on the file system on the array, It is. > eg. ext > works by trying to place files distant to each other to help reduce the > possibility of fragmentation? That's not relevant. What is relevant is where the filesystem metadata is stored, if any of it was lost when the disk died, and if the filesystem can recover itself with a repair operation. I know of one such recovery of a 60TB XFS filesystem residing on a combo mdraid linear array over 5 hardware RAID6 arrays, after 1 of the 5 constituent arrays suffered complete failure. xfs_repair deleted the entries from directory structure whose files were missing, allowing normal access to all other files. This was an extremely lucky outcome in this case and was only possible due to the specific on disk metadata layout of this individual filesystem. XFS would likely not be able to recover from such a failure in all cases. You're using EXT of some flavor. I suggest you read everything you can about the EXT version involved here, ask on the respective mailing list. Good luck. -- Stan