Re: Lots of SCSI-disks, how?!

Richard Gooch (Richard.Gooch@atnf.CSIRO.AU)
Wed, 22 Apr 1998 01:01:58 +1000


Fredrik Lindgren writes:
>
> Recently when we added some disks to our news server
> we stumbled on a slight problem...
>
> When adding devices for the disks, we found that you
> run out of minor numbers after /dev/sdp!
>
> How, if it's at all possible, do you circumvent this
> or is 16 the max number of disks you can have on Linux?

16 SCSI discs is the limit because the Linux SCSI implementation
supports 16 partitions per disc. With 8 bit minor numbers, you can
only fit 16*16 (256) partitions and discs on a SCSI system.

One "solution" is to increase the minor number size, but that has
problems with C library compatibilities. The correct solution IMHO is
to abandon the clumsy major&minor system altogether and use devfs,
which doesn't care about majors and minors.
I believe that Jakub Jelinek <jj@sunsite.ms.mff.cuni.cz> did some
hacking on the kernel to support more than 16 discs, if devfs is
available. It might be worth talking to him.

Regards,

Richard....

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