Rick Stevens wrote:
On Thu, 2007-08-09 at 18:58 -0500, Mikkel L. Ellertson wrote:
> From what I understand, there are a max of 16 device entries created
> for a SCSI hard drive. (sdx and sdx1 through sdx15) So while you can
> have more partitions then that, Linux will not let you access them
> when using the SCSI code to access the drive. I believe it is a
> driver problem more then a udev problem.
Well, the "x" in your example can take the RE form "[a-z]+". For
example, we have some storage arrays with, oh, 130 LUNs on them. They
appear as /dev/sda[1-15] through /dev/sdiv[1-15]
As far as the partition numbers, that's based on the minor number of the
block device. The formula is "(16 * drive number) + partition number".
The "16" is what limits it to 16 partitions (with partition 0 being the
same as the whole drive, e.g. "/dev/sda0" is the same as
"/dev/sda").
"man sd" will show you the magic.
You and I are saying the same thing, just in different ways. I used
x where you use [a-z]+. But I have never seen /dev/sda0 created. It
is always /dev/sda. You could also argue that the entire disk is not
a partition, even though you can access the entire disk as if it
were a partition. (You can create a file system on /dev/sda, but you
can not do that and have a partition table at the same time.) There
have been times in the past where I have used the entire drive
instead of creating a partition table. But most BIOS do not like it.
(Tar doesn't care - the drive can be one big archive.)
When you get into SCSI LUNs, you will probably lose a lot of people.
I have always found it easier to think of each LUN as its own
device. But then again, I worked more with CD drive arrays connected
to a LUN controller. 8 drives using one SCSI device number. Now
days, it usually works better to copy the CD images to a hard drive,
and loopback mount them. By using automount to manage them, you can
even keep the number of loopback mounts down to a reasonable number.
Mikkel
--
Do not meddle in the affairs of dragons,
for thou art crunchy and taste good with Ketchup!