xRAID disks....

[Matthew Seaman]

Erik Trulsson wrote:
> 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

It's rather easier and quite a lot less risky to simply do:

   # atacontrol delete ar0

	Cheers,

	Matthew

-- 
Dr Matthew J Seaman MA, D.Phil.                   7 Priory Courtyard
                                                  Flat 3
PGP: http://www.infracaninophile.co.uk/pgpkey     Ramsgate
                                                  Kent, CT11 9PW

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