Hard Disk configuration

[David A Higgen]

In article <9011051515.AA11388 at karron.med.nyu.edu>, karron at KARRON.MED.NYU.EDU writes:
> 
> I have a 780 MB scsi hard disk sitting on my desk from sgi I want to
> install.
> 
> Prior to calling the hotline, and due to the fact that I will not be
> at my desk today, I will put this question to the net-folks:
> 
> How do I plug the disk as scsi disk 2 (scsi disk 1 being the boot disk) ?
> 
> There are two banks of pluggable prongs, j8 and j7. There are also a
> jumber of jumper banks, jpnn. Which gets it. What about the terminator
> pack ?

Can't help you much with this one I'm afraid, I don't have a lot of contact
with SCSI disks at the hardware level & don't have the manual. You will
almost certainly want to remove the terminator; there should be only one
terminator on a SCSI bus.

> Once I get this put in, how do I make it appear as one continious disk,
> disk striping ?(Where did that name come from ?). 

I'm not exactly clear what you want to do. Do you mean make the new disk
and (part of) the root disk appear to be one logical disk? 

The IRIX 3.3 feature called 'logical volumes' can do this for you.
Read mklv(1M), lvtab(4), lv(7). There is also a section on this in the
System Administrator's guide. Also, for expanding an existing filesystem
when you have added a disk in this way, see growfs(1M).

Striping is one possible way of organizing a logical volume: it means that
storage is distributed between disks: the first 'n' blocks on disk 1,
the next 'n' on disk 2 etc. The idea being that you get more throughput
since the disks will be transferring concurrently.

However, if you want to join a disk to one containing an existing filesystem 
and enlarge the filesystem, you can't use striping since the disk where the 
existing filesystem resides isn't 'striped'! (So it would involve shuttling 
sections of data from the old disk to the new disk: too complex & error-prone 
to contemplate)!

> After having done that, what happens to the files when that disk 
> is not there ?

What would you expect? What happens to the files on any disk when it's not
there? They are, of course, not accessable. Note that if you have a logical
volume made up of more than one disk, all those disks must be present in
order to access the volume. 

Anyway, read the docs I mentioned, then if you have any more questions I'll
be glad to try to answer them by email.


			Dave Higgen (daveh at xtenk.asd.sgi.com)