xRAID disks....

Erik Trulsson ertr1013 at student.uu.se
Tue Jun 10 15:05:40 UTC 2008

On Tue, Jun 10, 2008 at 04:56:07PM +0200, Wojciech Puchar wrote:
> >
> > 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.
> there are no "raid hardware" on most devices. it's just marketing hype. 

Most (cheap) RAID controllers do almost everything in software. Some do have
hardware support.

> actually there is not much need to have it for RAID-0/1/10 where there is 
> almostnothing to process.

For mirrors it can actually be a big win with hardware support.
If you use software RAID then you will have to perform each write twice
(once to each disk), while with hardware support for RAID you only need
to transfer the data once.  If the controller resides on a PCI-bus together
with several other devices (which is not uncommon) then the reduced
bandwidth usage can be very useful.

(And for RAID you will need at least some support on the controller
if you want to be able to boot from a striped volume.)

> > 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?
> erase the whole drive.
> and next time don't use "hardware" RAID anymore. use gmirror and gstripe 
> to have PORTABLE RAID.

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

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