[SATLUG] 1st question - RAID5 quit - Short tests completed

Don Wright satlug at sbcglobal.net
Mon Aug 17 13:40:15 CDT 2009

On Mon, 17 Aug 2009 11:42:40 -0500, Jeremy Mann <jeremymann at gmail.com>

>Since only 1 drive is bad, why can't you just mark that drive as
>offline, shutdown the computer and put a new drive in, and hotadd the
>new drive to the array? This should start the rebuilding process

Jeremy & Sam: Right now mdadm thinks two out of four drives on the
RAID-5 are bad. There's a fair chance that the third drive only had a
small RAID hiccup and can be reinserted, but that hasn't been tested

David: Regarding /dev/sdc that failed the short test. First, power down
the system and disconnect the AC power cord at both ends.[1] Remove and
reattach the drive power cable and both ends of the data cable. This
will wipe the electrical contacts and should improve any intermittent
connection. If there is a SATA power adapter (short cable that connects
the old 4-pin power plugs to the new flat SATA power) then disconnect
and reconnect the 4-pin side of that, too. 

After reconnecting the drive power and data cables, semi-gently tug on
the individual wires of any 4-pin power connections. These can get loose
and deliver bad power. If you find any loose ones, disconnect them and
locate the side with the open barrel contact. You should see a gap along
one side so the metal looks like a nearly-closed 'c'. I generally use a
small screwdriver to reduce the diameter of the 'c' by gently wedging
the screwdriver between the metal and the plastic body. I go all around
the outside of the metal contact to attempt a uniform reduction in the
diameter. Reattach the 4-pin connector and try the tug test again. If
you still find loose contacts, repeat the procedure. If all is well, you
may reconnect the AC power cord and repeat the short test on /dev/sdc.

From the first post I conclude the data on the array is important to
you. To recover it I'd try SpinRite from www.grc.com. It's been saving
data for a long time, and the current release works with non-Windows
partitions. You need a Windows machine briefly to create a bootable
image on floppy, CD, or USB flash drive, but after that it's
self-contained. If this data is super-important and extremely difficult
to rebuild manually, then STOP NOW and start shopping for a drive
recovery service. You may not need to go this route if the other three
drives are OK, but we haven't gotten that far yet.

I have to run, so the others on this list can have at you for a while.
Please post the results of 
"mdadm --examine /dev/sda1 /dev/sdb1 /dev/sde1" for us to chew on.

[1] These instructions are (overly?) detailed because you (an
experienced system builder) are not the only one reading them.

A computer is a hole in your desk you pour time into.

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