From mboxrd@z Thu Jan 1 00:00:00 1970 From: Phil Turmel Subject: Re: How to recover after md crash during reshape? Date: Wed, 21 Oct 2015 08:18:12 -0400 Message-ID: <56278284.5020306@turmel.org> References: <04cdcd6bd69b3aa1f8f24465f8485c90@tantosonline.com> <874mhl2ed3.fsf@notabene.neil.brown.name> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <874mhl2ed3.fsf@notabene.neil.brown.name> Sender: linux-raid-owner@vger.kernel.org To: Neil Brown , andras@tantosonline.com, linux-raid@vger.kernel.org List-Id: linux-raid.ids Good morning Neil, On 10/20/2015 09:35 PM, Neil Brown wrote: > Nothing dumb about that - you don't need a --backup option. > If you did, mdadm would have complained. > > You only need --backup when the size of the array is unchanged or > decreasing. > mdadm reads the first few stripes and stores them somewhere in each of > the spares. md (in the kernel) then reads those stripes again and > writes them out in the new configuration. It appears that one of the > writes failed, others might have succeeded. This may not have corrupted > anything (the first few blocks are in the same position for both the old > and new layout) but it might have done. > If you do want to look for the backup, it is around about the middle of > the device and has some metadata which contains the string > "md_backup_data-1". If you find that, you are close to getting the > backup data back. Hmmm. This feature has advanced beyond my last look at the code. I was under the impression the backup option was only optional when mdadm could move the data offset. Does this new algorithm apply to v0.90 metadata, a v3.2 kernel, and v3.2.5 mdadm? Phil