I have 12 36-GB drives available for spool.

Based on recommendations made to this list earlier this year, I went
with 12 mirrored disk spools of 16 GB each (keep in mind disk
overhead).

As I understood it, the issue was you want many spools so that, as
Allen mentioned, you can have many threads for backups and even
migrations (assuming you have a good number of tape drives).

However, you don't want so many spools per disk, otherwise there is
contention for head movement on the drive which would result in
poorer performance.

johnn

=> On Thu, 26 Sep 2002 08:54:01 -0400, Mahesh Tailor
<MTailor AT CARILION DOT COM> said:

 Hopefully this is a simple question: I have fourteen 36GB drives that are
 available for the diskpool and I was wondering whether it is better to have
 seven 5GB files or three 10GB files or one 35GB file or something else?  The
 drives are mounted in two IBM-2014 Ultra-Wide SCSI disk drawers with
 separate Ultra-Wide contollers.  The other 14 drives are used for DB, LOG,
 and spare.

You have a total of 28 spindles, 14 each on two busses, right?

I'd suggest making a RAID-5 out of the fourteen free spindles, and then make
the individual volumes "A reasonable size".  What's a reasonable size?
Uh... ;)

I just did this with a drawer of 36G SSA, and I chose 10G volumes, because I
have about a dozen (and growing) disk pools amongst which I need to divide
things up.

Even if you only have one or two disk pools, it's useful to have more than a
few volumes per pool, because instantaneously only on thing can write to a
volume at a time.  So, for example, if you have 12 clients backing up, and one
70G disk volume, there is contention for the thread controlling that one
volume.

So calculate the size so that you'll have as many volumes as you feel like
keeping track of, but not many more than that.


- Allen S. Rout