Two sets of RAID1 drives - 16 partitions - naming?

[galahad7]

Hi there,

I've got two sets of RAID1 drives (four drives in total, two mirrors).

The number of RAID partitions across the two raid sets adds up to greater than 14, so I need more partition names.
For instance if there are 8 partitions on the first mirror and 8 partitions on the second mirror then I'm going to run out of numbers as Linux only allows a maximum of 14 or 15, i.e.
/dev/md1 /dev/md2 /dev/md3.... /dev/md14

So, am wondering if it is going to work if I create /dev/mda and /dev/mdb as follows:-
mknod /dev/mda1 b 9 1
mknod /dev/mda2 b 9 2
mknod /dev/mda3 b 9 3
....
mknod /dev/mdb1 b 9 1
mknod /dev/mdb2 b 9 2
mknod /dev/mdb3 b 9 3
...

Thanks for your help.
Stephen

[NeddySeagoon]

galahad7,

That idea is doomed because you all allocating the same major and minor device numbers to each set.
usr/src/linux/Documentation/devices.txt reads as if your should be able to have 256 raid devices as major block device 9 is only used for that purpose.

There may be a kernel limit, in which case you need a kernel patch.

You are not confusing the SCSI partition limit (15 max) with kernel raid limit are you ?
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

[galahad7]

[eccerr0r]

Another possible suggestion is to look into LVM with dynamically allocated major/minor numbers via device mapper - LVM partition names are arbitrary and you can have quite a few of them within the physical volumes (could even span the two RAIDs if you so desire.)

I'm running LVM with md-raid5. Though I only have a handful of partitions (Logical Volumes) the limit to the number of them is much more than I could ever use... Right now my logical volumes do not span physical volumes (or partitions) but I could... Vg0-l0 and Vg0-l1 are actually in the same RAID volume, /dev/md2.