Drive Failure on Software RAID

carlosinfl · 01-02-2011, 09:46 AM

My Linux server has two identical 750 GB SATA drives & I received notification that the server has experienced a drive failure on /dev/sda. Each identical drive has three partitions on it:

/dev/sda:

sda1 = swap
sda2 = /boot
sda3 = /

/dev/sdb:

sdb1 = swap
sdb2 = /boot
sdb3 = /

Then I have three /dev/md0-1-2 (Software RAID) partitions:

/dev/md0 = swap
/dev/md1 = /boot
/dev/md2 = /

Now you can see my failure listed below:

Code:

root ~ # cat /proc/mdstat 
Personalities : [raid1] 
      
md2 : active raid1 sdb3[1]
      731977536 blocks [2/1] [_U]
      
md1 : active raid1 sdb2[1]
      96320 blocks [2/1] [_U]
      
md0 : active raid1 sda1[0] sdb1[1]
      497856 blocks [2/2] [UU]
      
unused devices: <none>

So from above it appears that /dev/sda has failed and now is replaced by a new identical spare drive. My question is how do I force the new drive /dev/sda to synchronize and repair the RAID?

mostlyharmless · 01-02-2011, 10:04 AM

Sorry, I misread the question! How did you remove and replace the drive?

Does something like mdadm -a /dev/md2 /dev/sda3 not work?

carlosinfl · 01-02-2011, 12:20 PM

OK so I wanted to make sure I explain this:

I powered my server off and manually removed /dev/sda to emulate a drive failure. I powered the server back on and it booted fine however the RAID array was in a degraded state which is obvious since /dev/sda is missing. I then powered the server back off and re-added /dev/sda however the mdadm doesn't automatically initialize the drive. I had to manually re-add it with:

Code:

mdadm --manage /dev/md1 --add /dev/sda3
mdadm --manage /dev/md2 --add /dev/sda4

So now it appears to be re-synchronizing the mirror:

Code:

root ~ # cat /proc/mdstat 
Personalities : [raid1] 
      
md2 : active raid1 sda3[2] sdb3[1]
      731977536 blocks [2/1] [_U]
      [>....................]  recovery =  0.5% (4303744/731977536) finish=194.1min speed=62469K/sec

My question now is if this drive /dev/sda was completely brand new and didn't have any partition tables on it, would I need to create them on the newly replaced /dev/sda or should 'mdadm' simply be able to do it w/o me having to run fdisk.

brak44 · 01-02-2011, 02:56 PM

My question now is if this drive /dev/sda was completely brand new and didn't have any partition tables on it, would I need to create them on the newly replaced /dev/sda or should 'mdadm' simply be able to do it w/o me having to run fdisk.[/QUOTE]

You will need to use the sfdisk command to set up the partitions.
e.g. if sda is completely brand new

sfdisk -d /dev/sdb | sfdisk /dev/sda

will copy the partition info from sdb to sda

mostlyharmless · 01-02-2011, 03:49 PM

Agree with the above!