If you're not getting at least 15 GB/hr from your DLT7000 drive,
there's very likely some fixing that needs to be done.

At less than for DLT drive is not "streaming", which essentially means
the drive is wasting additional time on contant head repositioning. 
Below is my "quick and dirty" explanation of what happens when a
streaming-type tape drive doesn't get fed fast enough:

     1-incoming data stream begins

     2-tape spins up to write the incoming data

     3-the data buffer is written to tape

     4-look for more data, but it's not arrived yet!  (the tape is
spinning fast enough that we've gotten a bit ahead of ourselves at this
point)

     5-stop the tape, rewind to the last bit that got written

     6-go back to step 1 (or more likely step2, more data probably
arrived and piled up during step 4)


the end result is that your tape drive writes even more slowly than the
incoming stream of data.

The solution:  depends on the problem, but it's probably one or more of
the following:
    -tweaking the buffer sizes on the media server.  tweaking the
netbackup data buffers has been discussed at length on this list.
    -use of multiplexing
    -improvement of network bandwidth into the media server
    -use of FlashBackup (if your backup happens to be slow because of a
large number of small files)

HTH
rob

> -----Original Message-----
> From: Elrick, Sandy [mailto:Sandy.Elrick AT cdcgy DOT com]
> Sent: Thursday, October 18, 2001 11:44 AM
> To: 'veritas-bu AT mailman.eng.auburn DOT edu'
> Subject: [Veritas-bu] RE: Veritas-bu digest, Vol 1 #736 - 11 msgs
> 
> 
> 
> Hi Benr,
> 
> It seems like you are getting average speed.  At best I can get 10.5
> GB/hour
> (1750kb/s) on my systems.  This is the max capacity I've found of a
> DLT7000
> on a standard SCSI interface.  Is the DLT7000 on SCSI interface?
> 
> Sandy
> 
> Message: 8
> From: benr AT cuddletech DOT com
> Date: Wed, 17 Oct 2001 16:34:51 -0700 (PDT)
> To: <Veritas-bu AT mailman.eng.auburn DOT edu>
> Subject: [Veritas-bu] DLT7000 Speed
> 
> Any thoughts on this?  I'm doing some big backups to a DLT7000 (via a
> ADIC
> Scalar 2x tape robot).  My backup is 400G and running on a single
> drive.
> It's currently averaging 1500k/s.  The problem with this speed is
> that
> comes
> out to 5.4G/hr.  Isn't that alittle slow?  Can NetBackup throttle
> drives
> and
> thus slow down my backup this way?  Or is there something I can look
> to
> change?  The disk system on the system (this is a local backup) isn't
> really
> being taxed, and it's a Fibre Channel disk system with striped
> volumes.
> The system is a Sun Enterprise 4500 running Solaris 2.6 with
> NetBackup
> 3.2.
> 
> Thanx
> 
> benr.
> 
> _______________________________________________
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