Unplug sda (bad drive) and set the bios to boot to sdb, if it boots then it's a good drive.
Don't make any changes to the server, just test things out and shutdown.
Then test the other drive the same way.
Plug one drive in at a time and set the bios to boot to that drive.
You want to be sure you have the bad drive.
sda might boot and appear as ok when is by itself, doesn't mean it is.
Most important, mark good / bad on each drive, so you don't loose track of what your doing and before you start any destructive i.e. format command
wait 15 sec. and rethink all your steps.
Sure does look like sda md2 is the bad boy.
md2 : active raid1 sda2[2](F) sdb2[1]
732467520 blocks [2/1] [_U]
Check sata cable or scsi jumpers and mark it sda with a felt pen.
Doesn't mean the drive is bad, just give it a mfg diag format.
Once you know which drive for sure, then remove the good drive and mfg format the bad drive, MAKE SURE the good drive is unplugged.
Then there's no chance of formatting the wrong one.
You can also run mfg diag on it to test it.
You can put it back into sda and keep the bios set to boot to sdb.
Then server admin #5 manage raid.
About 30-60sec. it will start a rebuild, atl-f2 and login to watch the rebuild
watch -n .1 cat /proc/mdstat
oops EDIT:If you get this far then reboot after the rebuild and make sure you set the bios to boot sda.....not sdb.
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You could also do a manual restore of sda md2 partition from sdb, but if you make a mistake, your screwed, like forever.
Like if you restore (bad) sda md2 to (good) sdb md2 your screwed.
Plus you won't be able to re-format the entire drive and test it with mfg diag, the preferred method.
In short.... it's worth a try, might just be a corrupt sda md2
hth