Re: Increasing limit on SCSI hard drives

Jakub Jelinek (
Fri, 31 Jul 1998 11:42:30 +0200 (MET DST)

> Terry L. Ridder writes:
> > Hello;
> >
> > Since Informix & Oracle have joined the Linux Community
> > with their recent press releases it will be a matter of time
> > before the current limit of 16 SCSI hard drives poses a problem.

It poses the problem already, I'm running a 39 disk machine Linux machine
(using some older 2.1.9x kernel).

> >
> > Are there an plans to increase the limit to even 32 in the near
> > future?
> >
> > Is this type of enhancement scheduled for Linux-2.3?
> Jakub wrote a patch for the vger tree. It increased the size of dev_t
> to handle more discs, which required new syscalls, which then required
> new (patched) applications (like fdisk(8) and mount(8) IIRC).

It did not require patched applications, just upgrading libc (which already
has enough room for large dev_t and stuff like that in it's structures).
But the patch was not accepted by Linus, so it has been even removed from
the vger tree.
My friend is now working on adding 7 more majors to sd.c, so that we'll have
total 128 scsi disks, as Linus suggested when he refused to put the
xstat/xmknod patch in. Once that will be ready, he'll let you know.

> An alternative that doesn't require a change in dev_t size or changes
> to userspace is to use the automagic device number generation in
> devfs, and use the filp->private_data mechanism to distinguish
> partitions/drives. I've been planning on doing this, but haven't had
> time. I'd welcome a patch, though :-)

Even with this, sd.c has to have support for multiple majors, which current
does not have...

Jakub Jelinek | |
Administrator of SunSITE Czech Republic, MFF, Charles University
Ultralinux - first 64bit OS to take full power of the UltraSparc
Linux version 2.1.112 on a sparc64 machine (498.80 BogoMips).

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