Windows 2003 Server slow backup performance

ccosymx_at_hotmail.com
Date: 09/10/04 

Date: Fri, 10 Sep 2004 14:18:57 -0500

Something is causing extremely slow backup performance with our
Windows 2003 Server Standard Edition. The Windows 2003 Server
software is up-to-date. The machine it is running on is a Dell
Poweredge 1600SC, 2.4GHz, 2GB DDR 200MHz memory, 533MHZ FSB, 2-73GB
Ultra 320 SCSI hard drives. We ordered it with an Adaptec 39160 Ultra
320 SCSI controller card, and added a Sony TSL-S11000 DDS-4 Autoloader
external tape drive using an Adaptec 1838100 ACK-68V-68HD-LVD-2M
external 805A cable *which we had to buy separately) to connect the
Adaptec Controller Card to the tape unit.

We initially had major SCSI problems with this server, replaced the
SCSI backplane (hot swap, etc.), the tape unit, and one hard drive,
and finally fingered the other hard drive as the culprit. After
replacement, we could use the hard drives and the tape unit together
without errors. Except...

Using the built-in Backup program, writing to the tape drive is VERY
SLOW. I mean, 4.5GB (gigabytes) takes 3+ hours to write to tape, and
a verify takes another 3+ hours to accomplish. 49GB takes more than
12 hours. I am using Shadow Copy, and have set the Compress If
Possible Backup option set. It is consistently very slow.

The SCSI controller is using Ultra 320 to connect to the disk drives.
Due to our previous SCSI problems, we left the tape drive connecting
to the SCSI controller at 40Mb/s (megabits per second), but if I'm
doing the math right, I should be able to write 4.5GB (gigabytes) in
18 minutes, or 36 minutes if I assume I get only half the bandwidth -
way less than the hours I'm spending now. The Sony tape drive is
rated for a data transfer rate of 2.36MB/s uncompressed, SCSI burst
rate of 14MB/s max asynchronous, 40MB/s synchronous.

I can't find any errors in the event log, backups and verifies always
complete, and everything seems completely fine. The consistent
observed behavior is that the tape drive will write a little, then
just sit there doing nothing, then write a little (5-10 seconds), the
sit there, ad nauseum. Streaming if the tape is a far off dream; not
even close as it is now. The server is used only for file sharing for
10 people, and no other applications are being run on it. Processor
time is as much as a whopping 3% during a backup operation, so we are
not hammering the server into submission ever. No heavy disk activity
is observed either.

Is there some sort of "trickling" or other throttling going on that I
can turn off? Is there a way to monitor the SCSI bus for unreported
errors or other problems with the tape drive/hard drives or error
counters on the SCSI controller I can look at somehow to help me find
the problem? Any other wisdom I can use to try to improve things? Is
my math wrong?

Any thoughts, ideas, information, or further questions about our
configuration if I have forgotten a key piece of information, are
welcome.

Thanks for reading my question (which turned out to be lots more text
than I set out to produce, in the name of being thorough; sorry about
that).

Chris

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