Re: New filesystem for Linux

[Rene Herman <rene.herman@keyaccess.nl>]

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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