Alex - Thanks for that isolated example...good to see that kind of
thing.

I would caution against attributing the speed variation to the server
or tape drive until you have a bunch more information.  I'm no
Windows expert, but this kind of "pulsing" behavior might be an OS
issue where TCP buffers are quickly filled, then relatively slowly
drain, then quickly fill again...  I perceive that your client is
somewhere on the network, separated from the TSM server.  Depending
upon your networking, another possibility is bandwidth limiting,
where some sites may limit per-unit-time traffic; but that would be
unusual.  Whereas your server and client are both Windows, you might
perform the experiment of performing a test restoral of the 32 GB
data file locally on the server, to eliminate networking as a
variable and see how that performs.  You could eliminate the tape
drive variable by performing a test backup to a DISK or FILE type
stgpool, and restore from that.

Problem isolation in such cases can be tedious, but usually
determinable.  Whereas your server is a Windows 2000 OS, I'd be
conservative in expectations from that aged operating system, with
its known foibles.

   Richard Sims

On Dec 22, 2005, at 8:09 AM, Alexander Lazarevich wrote:

Thanks for the responses all, but it's not a tape mounting issue. I
wasn't
clear enough in my original post, but I am watching the actlog
while the
restore is taking place, and I'm sitting next to the library, so I can
tell when it's doing anything: remounting, rewinding, etc. What I'm
saying is this:

The server is restoring a single 32GB file, and starts doing so at
30+MB/sec. At some point, DURING the restore of that SAME 32GB
file, the
server suddenly slows down the restore, to 200-300K/sec. The server
has
NOT switched tapes, and is NOT rewinding even the SAME tape. It is
still
restoring that same 32GB file, but suddenly does so at a slower speed.

I know the drives have some kind of burst speed and normal speed.
Maybe
something is wacked out with that function?

Any other ideas?