Hi Clive,
> > > The limit to the number of logical partions is OS dependant. For
> > > IDE/SATA disks on Linux I'm pretty sure it's 64.
>
> I think John's right. Three usable primaries, the fourth primary is
> the extended one so isn't used directly but can contain up to 60
> logical partitions. So the kernel tracks 64 partitions, 63 of which
> can contain filesystems.
We've been chatting more about this on #dorset and now think that since
the merger of the IDE and SATA device driver in the kernel, which caused
the renaming of /dev/hda to /dev/sda, a new limitation is in place on
the number of logical partitions that can be accessed on a /dev/sd?
drive.
$ ls -l /dev/sd?
brw-rw---- 1 root disk 8, 0 2010-12-30 16:28 /dev/sda
brw-rw---- 1 root disk 8, 16 2011-01-13 16:32 /dev/sdb
$
The minor device number for each drive goes up in 16s. For /dev/sda,
we've
0 -- whole drive.
1-4 -- primary partitions, one of which may be extended and won't
appear in /dev.
5-15 -- logical partitions.
So the limit is 11 logical partitions. Your friend's error about the
17th partition may be down to 16 minor device numbers already being
taken, i.e. he had 9 logical partitions before he started the install, /
and swap took him to the maximum of 11, and /home then failed.
We also think nine logical partitions is quite a few and are curious as
to why there are so many. :-)
And yes, the hda -> sda migration does mean that drives with lots of
partitions being happily accessed yesterday now can't access some of
those later ones with a new kernel. Complainants are on the Internet.
Plus the Ubuntu install guide would seem to be wrong and out of date.
Cheers,
Ralph.
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