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SubjectRe: 520 byte sectors - any ideas?
Date
In linux.dev.kernel, article <01I4OVL7PA02EQOMZW@CRF.IT>,
a.vignani@crf.it writes:
>
> A friend of mine got an IBM662 SCSI hard disk coming from an IBM AS/400
> system and we tried to install and read it on a Linux system, to no avail.
>
> Seems that these disks are low-level formatted with a 520-byte sector
> size, which is correctly recognized by Linux on startup. [...]

Ahh. Somebody else had the bright idea to use 512-byte sectors plus a few
bytes for identifying the sector in case of crash.

It's a rather good idea, IMHO, except that it creates problems left and
right. (Left: Most disks can only be reformatted witzh powers-of-two sizes,
right: disks with weird block sizes don't work most other places.)



It should be possible to modify the SCSI driver to r/w the excess data
from/to some Random Area, given either an adapter which can do
scatter/gather or somebody who is willing to copy the block around once
again, but there's a better solution: Reformat.

> this is an unsupported size; Linux allows only 256,512 and 1024-byte
> sectors. There are so many >>9 and <<9 in the code I really doubt it
> could be easily modified.
>
Besides, anything with a sector size != 512 won't boot with LILO.

> Anybody out there had prior encounters with such disks? Any ideas?
>
Yes. Get a reasonable SCSI control/formatting program and reformat the
thing with 512-byte sectors.

Don't ask me which program to use -- whenever I have that problem, I just
grab the Mac laptop and startup HDT, a rather nice program to control just
about everything your disk can do.
--
Matthias Urlichs


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