From mboxrd@z Thu Jan 1 00:00:00 1970 From: James J Dempsey Subject: Re: raid1 missing disk Date: Thu, 12 Oct 2017 14:40:02 -0400 Message-ID: <380EE991-3AC6-43FE-87B1-A14CA2B53C7B@jjd.com> References: <85523B4D-6691-44F1-A609-A5280224E352@jjd.com> Mime-Version: 1.0 (Mac OS X Mail 10.3 \(3273\)) Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: linux-raid@vger.kernel.org Cc: James J Dempsey List-Id: linux-raid.ids > On Oct 12, 2017, at 12:48 PM, Reindl Harald wrote: >> > what do you mean by "I foolishly (physically) removed the disk before software removing it from the array”? I mean that I wasn’t thinking straight and the first thing I did was remove the disk and install the new disk without using mdadm to manage the array and remove the disk first. > if a disk explodes it also disappears unannounced Yes that’s true, and this is basically the same situation. > "My theory of this is that the computer switched it?s idea of which disk was /dev/sda and which was /dev/sdb as a result of the original removal" does not matter at all since you need the botaloader anyways on both (grub-install) and on a RAID1 it must not matter at all which is sda and wich is sdb, both can die at any point in time and both need to be bootable at any point in time Both are bootable. What I was talking about here was when I tried to resolve the problem by putting the failed disk back, the raid array started up and showed me the filesystem data before the raid failed the bad drive. I.e. it was not showing me the “good” “current” data presumably because it thought the “failed” drive was the other one. It was showing me the data from the drive it had previously failed. Thanks for your advice and thanks to Adam Goryachev for suggesting I just add the new disk to the array. I will try that. —Jim—