Re: Raid failing, which command to remove the bad drive?

["Timothy D. Lenz" <tlenz@vorgon.com>]

On 8/26/2011 3:45 PM, NeilBrown wrote:
> On Fri, 26 Aug 2011 13:13:01 -0700 "Timothy D. Lenz"<tlenz@vorgon.com>  wrote:
>
>> I have 4 drives set up as 2 pairs.  The first part has 3 partitions on
>> it and it seems 1 of those drives is failing (going to have to figure
>> out which drive it is too so I don't pull the wrong one out of the case)
>>
>> It's been awhile since I had to replace a drive in the array and my
>> notes are a bit confusing. I'm not sure which I need to use to remove
>> the drive:
>>
>>
>> 	sudo mdadm --manage /dev/md0 --fail /dev/sdb
>> 	sudo mdadm --manage /dev/md0 --remove /dev/sdb
>> 	sudo mdadm --manage /dev/md1 --fail /dev/sdb
>> 	sudo mdadm --manage /dev/md1 --remove /dev/sdb
>> 	sudo mdadm --manage /dev/md2 --fail /dev/sdb
>> 	sudo mdadm --manage /dev/md2 --remove /dev/sdb
>
> sdb is not a member of any of these arrays so all of these commands will fail.
>
> The partitions are members of the arrays.
>>
>> or
>>
>> sudo mdadm /dev/md0 --fail /dev/sdb1 --remove /dev/sdb1
>> sudo mdadm /dev/md1 --fail /dev/sdb2 --remove /dev/sdb2
>
> sd1 and sdb2 have already been marked as failed so there is little point in
> marking them as failed again.  Removing them makes sense though.
>
>
>> sudo mdadm /dev/md2 --fail /dev/sdb3 --remove /dev/sdb3
>
> sdb3 hasn't been marked as failed yet - maybe it will soon if sdb is a bit
> marginal.
> So if you want to remove sdb from the machine this the correct thing to do.
> Mark sdb3 as failed, then remove it from the array.
>
>>
>> I'm not sure if I fail the drive partition or whole drive for each.
>
> You only fail things that aren't failed already, and you fail the thing that
> mdstat or mdadm -D tells you is a member of the array.
>
> NeilBrown
>
>
>
>>
>> -------------------------------------
>> The mails I got are:
>> -------------------------------------
>> A Fail event had been detected on md device /dev/md0.
>>
>> It could be related to component device /dev/sdb1.
>>
>> Faithfully yours, etc.
>>
>> P.S. The /proc/mdstat file currently contains the following:
>>
>> Personalities : [raid1] [raid6] [raid5] [raid4] [multipath]
>> md1 : active raid1 sdb2[2](F) sda2[0]
>>         4891712 blocks [2/1] [U_]
>>
>> md2 : active raid1 sdb3[1] sda3[0]
>>         459073344 blocks [2/2] [UU]
>>
>> md3 : active raid1 sdd1[1] sdc1[0]
>>         488383936 blocks [2/2] [UU]
>>
>> md0 : active raid1 sdb1[2](F) sda1[0]
>>         24418688 blocks [2/1] [U_]
>>
>> unused devices:<none>
>> -------------------------------------
>> A Fail event had been detected on md device /dev/md1.
>>
>> It could be related to component device /dev/sdb2.
>>
>> Faithfully yours, etc.
>>
>> P.S. The /proc/mdstat file currently contains the following:
>>
>> Personalities : [raid1] [raid6] [raid5] [raid4] [multipath]
>> md1 : active raid1 sdb2[2](F) sda2[0]
>>         4891712 blocks [2/1] [U_]
>>
>> md2 : active raid1 sdb3[1] sda3[0]
>>         459073344 blocks [2/2] [UU]
>>
>> md3 : active raid1 sdd1[1] sdc1[0]
>>         488383936 blocks [2/2] [UU]
>>
>> md0 : active raid1 sdb1[2](F) sda1[0]
>>         24418688 blocks [2/1] [U_]
>>
>> unused devices:<none>
>> -------------------------------------
>> A Fail event had been detected on md device /dev/md2.
>>
>> It could be related to component device /dev/sdb3.
>>
>> Faithfully yours, etc.
>>
>> P.S. The /proc/mdstat file currently contains the following:
>>
>> Personalities : [raid1] [raid6] [raid5] [raid4] [multipath]
>> md1 : active raid1 sdb2[2](F) sda2[0]
>>         4891712 blocks [2/1] [U_]
>>
>> md2 : active raid1 sdb3[2](F) sda3[0]
>>         459073344 blocks [2/1] [U_]
>>
>> md3 : active raid1 sdd1[1] sdc1[0]
>>         488383936 blocks [2/2] [UU]
>>
>> md0 : active raid1 sdb1[2](F) sda1[0]
>>         24418688 blocks [2/1] [U_]
>>
>> unused devices:<none>
>> -------------------------------------


Got another problem. Removed the drive and tried to start it back up and 
now get Grub Error 2. I'm not sure if when I did the mirrors if 
something when wrong with installing grub on the second drive< or if is 
has to do with [U_] which points to sda in that report instead of [_U].

I know I pulled the correct drive. I had it labled sdb, it's the second 
drive in the bios bootup drive check and it's the second connector on 
the board. And when I put just it in instead of the other, I got the 
noise again.  I think last time a drive failed it was one of these two 
drives because I remember recopying grub.

I do have another computer setup the same way, that I could put this 
remaining drive on to get grub fixed, but it's a bit of a pain to get 
the other computer hooked back up and I will have to dig through my 
notes about getting grub setup without messing up the array and stuff. I 
do know that both computers have been updated to grub 2