15 partitions max prob revisited

15 partitions max prob revisited

[Keith Jacob]

When I first tried to install R4 (on a 7200/75) I ran into the prob of 
having too many partitions on my HD. Since I only use HFS (not HFS+), I 
partitioned my new 4GB drive into 8 Mac partitions (==max allowed by 
Drive Setup) totalling 2GB, and left the last 2GB for Linux. However, 
Linux would only allow me another 3 ext2 partitions, totalling 15 all up 
(4 Mac driver/patch &c., 8 HFS, and 3 ext2).

So the question is: can I add more devices (e.g. sdb16, sdb17, ...), or 
do I need to "reclaim" some HFS partitions if I want more ext2 ones? BTW, 
it was the installer that choked on the extra partitions I had created, 
so I would need to know how to fix that as well (if possible).

I'm sure this is not a Powermac/Linux prob, per se, but perhaps others 
have had this problem and found a neat fix for it (although HFS+ is not a 
solution for me until the Mac HFS+ disk tools improve).

Thanks in advance for any suggestions.

--
Keith Jacob
kjacob@wantree.com.au




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Re: 15 partitions max prob revisited

[Brad Boyer]

> So the question is: can I add more devices (e.g. sdb16, sdb17, ...), or 
> do I need to "reclaim" some HFS partitions if I want more ext2 ones? BTW, 
> it was the installer that choked on the extra partitions I had created, 
> so I would need to know how to fix that as well (if possible).
> 
> I'm sure this is not a Powermac/Linux prob, per se, but perhaps others 
> have had this problem and found a neat fix for it (although HFS+ is not a 
> solution for me until the Mac HFS+ disk tools improve).

No, this is a Linux problem.  You cannot have more than 15 partitions
on a drive because there are not device numbers allocated for anything
higher than partition number 15.  So even if you create a partion 16,
there is no way to access it under Linux.  This is the way that the
device numbers were allocated.  As far as I know, there isn't a
reasonable way to change this either.  Sorry I have to be the bearer
of bad news, but that's the way things currently stand.

       Brad Boyer
       flar@cegt201.bradley.edu

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Re: 15 partitions max prob revisited

[Ian K. Erickson]

On Tue, 19 Jan 1999, Brad Boyer wrote:
> No, this is a Linux problem.  You cannot have more than 15 partitions
> on a drive because there are not device numbers allocated for anything
> higher than partition number 15.  So even if you create a partion 16,
> there is no way to access it under Linux.  This is the way that the
> device numbers were allocated.  As far as I know, there isn't a
> reasonable way to change this either.  Sorry I have to be the bearer
> of bad news, but that's the way things currently stand.

Not that know anything about it, but out of curiosity: couldn't you use
mknod to create >15 [hs]da's? Or could you recompile the kernal to allow
them?

Ian K. Erickson                 iPEG, the Internet Productivity Group
Systems Administator            W 422 Riverside, Suite 628
ian@ipeg.com                    Spokane, WA 99204
http://www.ipeg.com             (509)462-iPEG

4F6E65204F5320746F2072756C65207468656D20616C6C2C204F6E65204F5320746
F2066696E64207468656D2CDA4F6E65204F5320746F206272696E67207468656D20
616C6C20616E6420696E20746865206461726B6E6573732062696E64207468656D 


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Re: 15 partitions max prob revisited

[Brian Downing]

On Tue, 19 Jan 1999 11:51:15 -0800 (PST), "Ian K. Erickson" writes:
 > On Tue, 19 Jan 1999, Brad Boyer wrote:
 > > No, this is a Linux problem.  You cannot have more than 15 partitions
 > > on a drive because there are not device numbers allocated for anything
 > > higher than partition number 15.
 > 
 > Not that know anything about it, but out of curiosity: couldn't you use
 > mknod to create >15 [hs]da's? Or could you recompile the kernal to allow
 > them?

No.  It works like this:

brw-rw----   1 root     wheel      8,   0 Sep 12  1994 /dev/sda
brw-rw----   1 root     wheel      8,   1 Sep 12  1994 /dev/sda1
brw-rw----   1 root     wheel      8,   2 Sep 12  1994 /dev/sda2
...
brw-rw----   1 root     wheel      8,  14 Sep 12  1994 /dev/sda14
brw-rw----   1 root     wheel      8,  15 Sep 12  1994 /dev/sda15

...so partition 16 would be major 8 minor 16, except:

brw-rw----   1 root     wheel      8,  16 Sep 12  1994 /dev/sdb
brw-rw----   1 root     wheel      8,  17 Sep 12  1994 /dev/sdb1
brw-rw----   1 root     wheel      8,  18 Sep 12  1994 /dev/sdb2

If we had more device nodes to play with, we could have devices that
work per SCSI id instead of the dynamically allocated ones we have now.
It's a huge pain when you remove a disk on a server and sdf-sdk fall
down to sde-sdj.  Or worse -- when a faulty disk falls off the chain,
and when the (unsupervised) machine reboots -- everything is mounted in
the wrong place!  :-)

-bcd
--
**               Brian Downing
**  UNIX Systems Administrator
**        bdowning@wolfram.com

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Re: 15 partitions max prob revisited

[Paul Mackerras]

Keith Jacob <kjacob@wantree.com.au> wrote:

> So the question is: can I add more devices (e.g. sdb16, sdb17, ...), or 
> do I need to "reclaim" some HFS partitions if I want more ext2 ones? BTW, 
> it was the installer that choked on the extra partitions I had created, 
> so I would need to know how to fix that as well (if possible).

The problem is in the encoding of the device minor number for scsi
disks: only 4 bits are allocated to the partition number, so you can
have at most 15 partitions (/dev/sdx uses partition number 0).

Paul.

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