I've been playing with RAID 1 in my new file server. I created a RAID 1 array out of two identical 3 TB drives, and everything was working fine. I then wanted to see if the mirroring was actually working, so i turned off the computer, unplugged one of the drives, and turned the computer back on.

At startup, I got a bunch of errors about the RAID array not being all present and asking if I wanted to start it degraded. I said yes. The system booted up and my files were still there. Yay!

I turned the computer off, plugged the drive back in, and booted. Still got the same error about the array being degraded. So, I issued the command

and got an error that sdb1 was not a member of an array. Anyone know why? I gather that mdadm marked it as gone but don't understand why it wasn't able to realize that sdb1 was still the same RAID component that had always been there.

Now, I'm just re-adding it to the array the slow way: as if it were a brand new drive, which seems to be working.

Says it'll take about 6 hours to finish. I'd appreciate any color on what happened and how I might have re-added it more painlessly.

Thanks!

The array probably isn't using a bitmap. See, for example:

http://ubuntuforums.org/showthread.php?t=1283619

Ahhh...thanks! I had no idea. Oh well, now I need to wait 2700 minutes for the resync to complete. I think it slowed down a lot because I'm using files on the array while it's resyncing.

As they say on the GEICO commercials - everybody knows that.

Whatever the hell it is you're talking about.