Topic: RAID1 UU_?

[Mirfster]

Sorry if this seems like a silly question, but for the life of me I simply cannot figure out what is missing from the RAID Array.  I have read the "RAID" and "Manual Rebuild" WIKIs, but still am at a loss.  The fact that it shows me "[UU_]" has got me confused.

Here is what I ran:

cat /proc/mdstat
Personalities : [raid1]
md1 : active raid1 sdb1[1] sda1[0]
      104320 blocks [3/2] [UU_]

md2 : active raid1 sdb2[1] sda2[0]
      1465031488 blocks [2/2] [UU]

unused devices: <none>

So I checked MD1:

mdadm --query --detail /dev/md1
/dev/md1:
        Version : 0.90
  Creation Time : Thu May 10 22:59:26 2012
     Raid Level : raid1
     Array Size : 104320 (101.89 MiB 106.82 MB)
  Used Dev Size : 104320 (101.89 MiB 106.82 MB)
   Raid Devices : 3
  Total Devices : 2
Preferred Minor : 1
    Persistence : Superblock is persistent

    Update Time : Tue Jul 31 02:24:46 2012
          State : clean, degraded
 Active Devices : 2
Working Devices : 2
 Failed Devices : 0
  Spare Devices : 0

           UUID : db3b369e:2d138085:69e1c4c9:c8b20f28
         Events : 0.92

    Number   Major   Minor   RaidDevice State
       0       8        1        0      active sync   /dev/sda1
       1       8       17        1      active sync   /dev/sdb1
       2       0        0        2      removed

I can "fail remove and add" both /dev/sda1 and /dev/sdb1 so they can rebuild (which I did), but I have no idea what the "_" is in the "UU_" or how to determine this..

System is a RAID1 (with Spare...supposedly). After failing, removing and then adding sda1 and sdb1 it rebuilds.  However, after rebooting I am getting the e-mail message:

A DegradedArray event has been detected on md device /dev/md1

Any ideas on what I am missing here would be greatly appreciated.

[newburns]

Are you saying that one of the drives failed, then you rebuild the array, and are wondering why the UU_ is shown?

Or are you saying that you installed SME and, afterwards, it showed UU_?
I have only ran into that second case before, and it was because I had a USB drive attached. I was trying to do a restoration, but after installation it said that there was no restoration file on there. So I proceeded with installation, only to find that the installation included the USB drive as part of the raid array.

Other than that, I'm not sure what else it could be. But BEWARE, clean installs will format your attached USB disk.

[Mirfster]

Correct one of the drives failed.  I replaced the drive and that is when I noticed the "UU_".  Didn't see it before.

Thanks.

[newburns]

I have noticed this with my current array. I have 6 2tb drives, and one failed. It's a raid5 with spare, and when the one drive failed, md2 had a degraded array. It took a while before md1 was degraded. Actually, md1 didn't show the failed /dev/sdf until after md2 array was rebuilt.
What I believe has happened:
md2 showed a failed device, so you removed and replaced failed drive.
md1 didn't show that device has failed, so the drive was removed from a clean raid causing it to be degraded.
The new drive was automatically added to md2 and md1 since they were degraded, but md2 replaced a failed drive, while md1 added a new drive and still awaiting the status of the removed drive.

I am not sure how to remove the previous drive from the md1 array to where it will be UU and not UU_.