View Full Version : [ubuntu] Ubuntu Server 64 Software RAID dropped drive at start up.

December 17th, 2010, 04:01 PM
I have 5 2 TB drives in software RAID 5 that I created in Webmin. Every now and again when I start my system one of these drives does not "come up" and the RAID 5 is not active. It is still mounted as I can get to and see the data. Webmin shows it as not active and the drive space shows it is shy of 1 drive. There is no indication of which drive is missing!

I tried mdadm -D /dev/md1 to look at which drive was not present, but it gave me an error of something like "md1 is not active so I can't look at it"

Stopping md1 and rebooting usually helps bring it back to life.

I think it is the same drive that keeps falling out. I would like to replace this drive while I can still get a new replacement from Newegg and not a refurb from Samsung.

By polling the drives with SMART, I know which drive is in which bay - by serial number and by" device a" "device b", etc. (I have patched my firmware to fix the issue with the HD204UI 2TB drives.) I just don't know how to tell that serial number xyz or "device x" is the one that I need to take a look at.

How do I tell what drive has failed?

Thanks in advance!


December 17th, 2010, 10:29 PM
Find out what /dev/sd* drive keeps failing and then do

hdparm -i /dev/sd*

It will tell you a SerialNo. This SerialNo should also be printed at the drive physically.

December 18th, 2010, 03:33 AM
That is the issue, I do not know how to figure out which drive keeps dropping out. I know which SN is in which bay, so if I can figure out it is sdg for example, I know it is the drive in bay 4.

How do I tell if it is sda or sdb etc?


December 18th, 2010, 01:53 PM
What does

cat /proc/mdstat
has to say?

December 19th, 2010, 10:55 PM
When the drive drops, I can't pull info from mdstat since it says it is inactive.


December 20th, 2010, 03:01 PM
Ok nasty. I don't think it is the best option but the only thing I can think of now is: unplugging each drive until you got a clean boot. Then you have the 'bad one' disconnected.

Don't you get more information at boot? Logs? There must be a kinds of error I guess.

December 20th, 2010, 04:50 PM
You would think that Linux would tell you what drive has failed. How am I to know?? What if I had 30 drives in there? I must be missing something as there has got to be a way for software RAID to tell you what drive failed.

RAID Guru's, what is your take on this?


December 20th, 2010, 05:47 PM
Did you search for logs?

Other option: Boot to Live CD and assemble the array. This Live CD will also allow you to read S.M.A.R.T. data via Disk Utility (GUI).

December 21st, 2010, 01:52 AM
Yes, I did search the logs, but I did not find anything. I bet I am not looking in the correct log though.


December 22nd, 2010, 05:26 AM
What is the output of the following commands?
replace /dev/md0 with the path of your raid device.

sudo mdadm --detail /dev/md0
cat /proc/mdstat