From mboxrd@z Thu Jan 1 00:00:00 1970 From: "David C. Rankin" Subject: Re: How best to re-sync raid1 array? zero superblock on removed disk and let it rebuild? Date: Fri, 28 Aug 2015 04:42:58 -0500 Message-ID: <55E02D22.802@suddenlinkmail.com> References: <55E02841.9050701@suddenlinkmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <55E02841.9050701@suddenlinkmail.com> Sender: linux-raid-owner@vger.kernel.org To: mdraid List-Id: linux-raid.ids On 08/28/2015 04:22 AM, David C. Rankin wrote: > All, > > I had a disc-controller failure on a server running several raid1 arrays. The > disks are fine, but I have had the root partition come up in degraded mode. What > is the best way to tell mdraid to resync the disks? Here are the symptoms: > > # cat /proc/mdstat > Personalities : [raid1] > md1 : active raid1 sdb7[1] > 52396032 blocks super 1.2 [2/1] [_U] > > md3 : active raid1 sdb6[1] sda6[0] > 1047552 blocks super 1.2 [2/2] [UU] > > md2 : active raid1 sda8[0] sdb8[1] > 922944192 blocks super 1.2 [2/2] [UU] > bitmap: 0/7 pages [0KB], 65536KB chunk > > md0 : active raid1 sda5[0] sdb5[1] > 204608 blocks super 1.2 [2/2] [UU] > > unused devices: > > # mdadm --misc --detail /dev/md1 > /dev/md1: > Version : 1.2 > Creation Time : Wed Nov 27 04:35:49 2013 > Raid Level : raid1 > Array Size : 52396032 (49.97 GiB 53.65 GB) > Used Dev Size : 52396032 (49.97 GiB 53.65 GB) > Raid Devices : 2 > Total Devices : 1 > Persistence : Superblock is persistent > > Update Time : Fri Aug 28 04:12:18 2015 > State : clean, degraded > Active Devices : 1 > Working Devices : 1 > Failed Devices : 0 > Spare Devices : 0 > > Name : archiso:1 > UUID : 320d86f7:22999af5:5eeefee1:35cd8970 > Events : 100308 > > Number Major Minor RaidDevice State > 0 0 0 0 removed > 1 8 23 1 active sync /dev/sdb7 > > Reading, it looks like one approach is the boot the install media and then zero > the superblock on /dev/sda7 and then reboot. Will that force a rebuild, or do I > need to fail and remove the disk first? I was thinking: > > # mdadm --zero-superblock /dev/sda7 > > should set it up for a rebuild without more. Is this a sane approach? > This adds a bit more of the picture. It's like sda7 doesn't even know it was kicked out. There are no disk errors logged for either of the drives: # mdadm -E /dev/sd[ab]7 /dev/sda7: Magic : a92b4efc Version : 1.2 Feature Map : 0x8 Array UUID : 320d86f7:22999af5:5eeefee1:35cd8970 Name : archiso:1 Creation Time : Wed Nov 27 04:35:49 2013 Raid Level : raid1 Raid Devices : 2 Avail Dev Size : 104792064 (49.97 GiB 53.65 GB) Array Size : 52396032 (49.97 GiB 53.65 GB) Data Offset : 65536 sectors Super Offset : 8 sectors Unused Space : before=65448 sectors, after=0 sectors State : active Device UUID : f5a48ea1:bce2f6f0:f47f9c0b:bad1d64d Update Time : Sat Aug 8 17:17:21 2015 Bad Block Log : 512 entries available at offset 72 sectors - bad blocks present. Checksum : 2c45bcef - correct Events : 280 Device Role : Active device 0 Array State : AA ('A' == active, '.' == missing, 'R' == replacing) /dev/sdb7: Magic : a92b4efc Version : 1.2 Feature Map : 0x8 Array UUID : 320d86f7:22999af5:5eeefee1:35cd8970 Name : archiso:1 Creation Time : Wed Nov 27 04:35:49 2013 Raid Level : raid1 Raid Devices : 2 Avail Dev Size : 104792064 (49.97 GiB 53.65 GB) Array Size : 52396032 (49.97 GiB 53.65 GB) Data Offset : 65536 sectors Super Offset : 8 sectors Unused Space : before=65448 sectors, after=0 sectors State : clean Device UUID : 66e069cc:02daa93e:1d4a6eea:e5c21cb7 Update Time : Fri Aug 28 04:35:31 2015 Bad Block Log : 512 entries available at offset 72 sectors - bad blocks present. Checksum : ed07de3b - correct Events : 100584 Device Role : Active device 1 Array State : .A ('A' == active, '.' == missing, 'R' == replacing) Do I try a --re-add on sda7 or just zero it for a complete rebuild? Any help appreciated. -- David C. Rankin, J.D.,P.E.