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SubjectRe: New filesystem for Linux
H. Peter Anvin wrote:

> Rene Herman wrote:

>> For primary (and extended) partitions, yes. I haven't used any version
>> of DOS that has ever objected to arbitrarily aligned partitions in the
>> MBR (and I do align them arbitrarily since I always make my partitions
>> some exact size and start the next partition in the next sector).
>>
>> Different though for logical partitions inside an extended. As late as
>> Windows 98, DOS would object to non-aligned logicals, at the very
>> least with some settings for the BIOS use/don't use LBA or "Large"
>> settings.
>>
>> Linux doesn't care; I've used type 0x85 instead of 0x05 for my
>> extended partitions dus to that for years. DOS just ignores that one...
>>
>
> DOS, or FDISK?

DOS. It was something like DOS accepting the non cylinder-aligned
logical but then proceding as if it were cylinder aligned anyway,
rounding the starting sector down. This obviously is not good.

Also see the "--DOS-extended" comment in the sfdisk man page. Since I do
remember differences when using different "Large" CHSs in the BIOS, for
all I remember I was experiencing that problem when I ran into it. If
so, the DOS underlying Windows 98 is among the "some versions".

In any case, yes, non-cylinder aligned logical partitions (for whichever
defintion of "aligned" fits DOS' idea of the geometry) really do cause
trouble.

The DR-DOS (-> Novel DOS -> Caldera OpenDOS) warning in that manpage
seems to imply that cylinder alignment was a good idea for all
partitions seen by it, and I do remember it being a pain in that regard
as well. Guess it's pretty safe to not care about DR-DOS anymore though.

Rene.
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