Filesystem device node files

[Geoff Rainey (DSL AK)]

Hello,

I would like to know how filesystem device node files get allocated.
For instance, I have a RHAS 2.1 box connected to a SAN which presents 
the SAN volumes. It seems with differing kernel versions, the SAN 
volumes are configured on different device node files, under one version 
of kernel, they are /dev/sdb1 and /dev/sdb2, then under another kernel 
version, they become /dev/sdd1 and /dev/sdd2, and /dev/sdb1 and /dev/sdb2 
are no longer devices at all. 
Can anyone describe to me why this occurs, or show me a document 
describing this?

Regards,
Geoff Rainey.