strange error of GEOM_RAID3 on RELENG_5

[Hiroki Sato]

Pawel Jakub Dawidek <pjd at FreeBSD.org> wrote
  in <20050324135602.GZ591 at darkness.comp.waw.pl>:

pj> This is very strange and I've no idea why you get EPERM from ad[246]s1a.

 Ah, I found a simple use of dd failed.  Sorry for the false alarm...

 I used a disklabel like this:

 a:   100g      *    4.2BSD
 c:    *        *    unused

 When the offset of /dev/ad2s1a is 0,
 "dd if=/dev/zero of=/dev/ad2s1a bs=512 count=1" works fine but
 "dd if=/dev/zero of=/dev/ad2s1a bs=512 count=2" fails (count > 2 or
 bs!=512 also occurs EPERM with whatever skip= value).
 When the offset is set to >2, dd works as expected.

 The second sector seems to contain the disklabel information
 and "disklabel -w /dev/ad2s1a auto" generates an offset
 of 16 for a: partition.  Is using an offset of 0 wrong?
 I assumed that the offset can be 0 and /dev/ad2s1a does not
 (effectively) overlap with the disklabel area and so on,
 but am I mistaken about it?

 And if the offset is necessary, I still do not understand why
 "dd if=/dev/zero of=/dev/ad2s1a bs=512 count=2 skip=1000" fails.

-- 
| Hiroki SATO
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