raid 1 recovery steps

raid 1 recovery steps

[chapman]

Sorry for the noob question but I want to make sure I get this right.

I have a raid 1 (sata) running on an active server - mdadm reports sda1 as
faulty.  Running "mdadm --examine /dev/sda1" shows the state as dirty, no
errors - no failed devices.  Can I assume the disk is ok, just needs to be
re-added to the array?

I'm assuming I need to first remove sda1 from the raid then re-add it,
correct?  If so, what are the specific steps?  Can this be done safely on a
live server without pulling the system down?  How will this affect rebooting
once completed - if at all?  Any gotchas I should look out for?


Here's some mdadm output...

/sbin/mdadm --detail /dev/md0
/dev/md0:
        Version : 00.90.00
  Creation Time : Thu Jan 27 09:55:22 2005
     Raid Level : raid1
     Array Size : 154183680 (147.04 GiB 157.88 GB)
    Device Size : 154183680 (147.04 GiB 157.88 GB)
   Raid Devices : 2
  Total Devices : 2
Preferred Minor : 0
    Persistence : Superblock is persistent

    Update Time : Wed Sep 13 01:45:03 2006
          State : dirty, no-errors
 Active Devices : 1
Working Devices : 1
 Failed Devices : 1
  Spare Devices : 0


    Number   Major   Minor   RaidDevice State
       0       8        1        0      faulty   /dev/sda1
       1       8       17        1      active sync   /dev/sdb1
           UUID : 49f6e41a:28dde75c:8f133fe5:823322fb
         Events : 0.40



/sbin/mdadm --examine /dev/sda1
/dev/sda1:
          Magic : a92b4efc
        Version : 00.90.00
           UUID : 49f6e41a:28dde75c:8f133fe5:823322fb
  Creation Time : Thu Jan 27 09:55:22 2005
     Raid Level : raid1
    Device Size : 154183680 (147.04 GiB 157.88 GB)
   Raid Devices : 2
  Total Devices : 2
Preferred Minor : 0

Update Time : Wed May 24 04:59:32 2006
State : dirty, no-errors
Active Devices : 2
Working Devices : 2
Failed Devices : 0
Spare Devices : 0
Checksum : bce563ef - correct
Events : 0.39


      Number   Major   Minor   RaidDevice State
this     0       8        1        0      active sync   /dev/sda1
   0     0       8        1        0      active sync   /dev/sda1
   1     1       8       17        1      active sync   /dev/sdb1


TIA for any assistance you can provide.

--chapman
-- 
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Re: raid 1 recovery steps

[Tuomas Leikola]

On 9/24/06, chapman <chris@datasetgo.com> wrote:
> Can I assume the disk is ok, just needs to be
> re-added to the array?

Not necessarily. You should look for logs indicating _why_ it is
marked bad. If you don't know how long it's been broken, you need some
monitoring system, like mdadm or logcheck.

This is most commonly caused by bad sectors. If you can re-add and
resync goes through without complaining, you're probably ok.

> I'm assuming I need to first remove sda1 from the raid then re-add it,
> correct?  If so, what are the specific steps?

mdadm /dev/md0 -r /dev/sda1
mdadm /dev/md0 -a /dev/sda1

> Can this be done safely on a
> live server without pulling the system down?

sure.

> How will this affect rebooting
> once completed - if at all?

Should not have any impact. At least if boot setup is ok.

> Any gotchas I should look out for?

Things get tricky if the other disk has stealthily become bad.

- tuomas