xRAID disks....

[Erik Trulsson]

On Tue, Jun 10, 2008 at 04:33:47PM +0200, DA Forsyth wrote:
> Hiya
> 
> I've had this for a while now and have done many searches for info 
> but have not yet come up with the right question, hence have not got 
> the answer.
> 
> My main server has an Adaptec IDE raid card.  A couple of years ago I 
> took disks that had been a mirror pair on that card out of the server 
> and put them into my test server, not as a raid pair since the test 
> server has no raid hardware.
> 
> During boot I see this
> ad0: 19092MB <WDC WD200EB-00CPF0 06.04G06> at ata0-master UDMA66
> ad1: 76319MB <WDC WD800JB-00ETA0 77.07W77> at ata0-slave UDMA66
> ad2: 76319MB <WDC WD800JB-00ETA0 77.07W77> at ata1-master UDMA66
> ad3: 19092MB <WDC WD200EB-00CPF0 06.04G06> at ata1-slave UDMA66
> ar0: 76319MB <Adaptec HostRAID RAID1> status: BROKEN
> ar0: disk0 DOWN no device found for this subdisk
> ar0: disk1 DOWN no device found for this subdisk
> 
> The pair of ex-RAID disks are ad1 and ad2 and obviously are no longer 
> a raid pair, yet 'something' is telling the ar() driver to try and 
> pair them and failing because there is no raid hardware in that box.
> 
> Now I am reconfiguring that machine a bit and would like to fix this, 
> both on these existing drives and on the 320MB drive I have just 
> removed from a RAID1 pair and will be putting into the box instead of 
> ad3 (the other 320GB from the pair is in a USB enclosure for other 
> purposes and has not shown any signs of knowing it was in a raid 
> pair)
> 
> I suspect the raidinfo is stored on the disk somewhere and a suitable 
> 'dd' command can erase it.  but where and how?

That kind of information is usually stored last on the disk (where it is
least likely to be overwritten by filesystems, partitioning info, or boot
loaders), so if you overwrite the last couple of KBs on those disks you will
probably be fine.
(If you want to be certain you can always use 'dd' to nuke all the
information on the disk.  That will take longer time, but you get the extra
advantage of testing all the blocks on the disk so that they work
correctly.)

For the first you could do something like:
 dd if=/dev/zero of=/dev/ad1 bs=1m skip=76318
which should overwrite the last MB of ad1 with zeros.

To erase all of the disk:
dd if=/dev/zero of=/dev/ad1 bs=1m



-- 
<Insert your favourite quote here.>
Erik Trulsson
ertr1013 at student.uu.se