Undeletable ATA RAID

[Soeren Schmidt]

It seems Sean Hamilton wrote:
> | Hmm, with both disks connected, atacontrol delete whatever arrays it
> | see there, then make a new array with atacontrol covering both disks,
> | then delete that. That should make certain all array information si
> | overwritten...
> I can't, because the second disk is gone. (I probably should have deleted
> the array before removing it...) I could add another disk, or whatever, but
> this problem should probably be fixed.

Then just do it on the part that is there.

> Anyhow, sequence of events:
> 
> - Create SPAN array ar0 on ad4,ad6. (the only disks in the system)
> - Install freebsd onto array.
> - Get new disks, install as ad0 and ad1.
> - Create stripe ar1 on ad0,ad1.
> - Forgetting having done so, remove ad1.
> - Boot, now ar0 and ar1 are reversed. ar0 is broken, ar1 works fine
>   (but fstab is confused, of course.)
> 
> It can boot fine if I unplug ad0, so I'm guessing it looks at the first disk
> for raid info? Hm, perhaps a better naming system is in order. I never liked
> how it stores array info in the disk like this... seems trouble-prone...
> like this.

Well, the arrays are numbered in the sequence they are found..

> ...Ah, seems booting into single-user, deleting ar0, creating at0 as a
> single-disk span array, and deleting that, has things working. Where does it
> store the array info? Seems strange that zeroing the disk kept it, does it
> just choose a disk and use that for all info? Or is it at the end of the
> disk? I ^Cd the dd after a few seconds.

For a Promise ATA RAID the config info is at MAXLBA-63 and the info is on
*all* disks in the array.

-Søren