On Wednesday 02 April 2003 04:18 am, Roman Zippel wrote:
> Hi,
>
> On Mon, 31 Mar 2003, Badari Pulavarty wrote:
> > I have been playing with supporting 4000 disks on IA32 machines.
> > There are bunch of issues we need to resolve before we could
> > do that.
> >
> > I am using scsi_debug to simulate 4000 disks. (Ofcourse, I had
> > to hack "sd" to support more than 256 disks).
>
> Could you please post your changes to sd.c and anything relevant to it?
> Thanks.
>
> bye, Roman
Roman,
Here is the patch for sd to allow more than 256 disks.
There are few issues with the patch that need to be resolved.
1) With the patch I get 16 bits for minor. Since 4 bits are used for
partition, we get 12 bits to represent disks. So each major can support
2^12 = 4096 disks. Disks 0 - 4095 are mapped to major=8,
disks 4096 - 8191 to major = 65 and so on..
This means ..
(i) I need to create nodes in /dev/ to match new <major, minor> for
these disks. Currently "mknod" is broken due to glibc issues with dev_t.
(ii) We need to worry about backward compatibility. For example:
17th disk used to have <65, 0>. Now its major, minor is <8, 256>.
So /dev/ entires need to be re-created to match these, everytime
you reboot 2.4/2.5 etc. Greg KH udev might fix this for us.
2) Do we still need 16 majors for disks ?
We could change my patch to work around major/minor assignment
issues and maintain backward compatibility.
Thanks,
Badari
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This archive was generated by hypermail 2b29 : Mon Apr 07 2003 - 22:00:16 EST