Thanks for the info Austin.  You pretty much confirm what I have been reading.

Anyone else have an idea of why I can only seem to drive the tape drives at 
12.5MB/sec when duplicating tapes on the master server?  The server itself is 
not loaded during this activity.  It seems that bpduplicate should be able to 
read at max speed and write at max speed simultaneously especially since the 
drives and server are connected over a 2gb/sec SAN.

I guess the long-term solution is to go with a disk-based device (such as the 
Data Domain) for the initial backups and then archive to tape from there.

Also, what about the bpduplicate performance when duplicating multiplexed 
tapes?  How about restores from the same?  Am I just moving the bottleneck from 
one place to another?

Any links to info that will educate me on the subject are appreciated.

Thanks again,
Steve.

> -----Original Message-----
> From: Austin Murphy [mailto:austin.murphy at gmail.com]
> Sent: Thursday, December 21, 2006 7:24 AM
> To: Steve Kirkpatrick
> Cc: veritas-bu at mailman.eng.auburn.edu
> Subject: Re: [Veritas-bu] LTO-3 throughput expectations
> 
> 
> On 12/21/06, Steve Kirkpatrick <skirkpatrick at ghx.com> wrote:
> > NB5.0MP6
> > Master server: Sun V440 w/ 4x1.2GHZ SPARC III, 8GB RAM 
> running Solaris 10
> > Sun L500 library with four HPUltrium LTO-3 drives connected 
> to master server
> > via 2GB SAN.
> >
> > I can't seem to get more than 12.5MB/sec throughput on 
> these LTO-3 drives.  That
> > is about the same as I am getting on another server's 
> SCSI-connected LTO-1 drives.
> > I see the same performance whether I am duplicating tapes 
> using bpduplicate or
> > when I am backing up clients over a gigabit network.
> >
> > After reading all of the recent threads concerning tape 
> drive performance,
> > shoeshining, etc, I can't believe that the master server is 
> only able to feed
> > 12.5MB/sec of data to these drives.
> 
> You bottleneck is most likely the network and/or the source system.  A
> gigabit network maxes out at 35 MB/sec in some cases. Getting better
> than 50 MB/sec is rare.
> 
> > Some of the previous threads on the subject suggested 
> multiplexing jobs across
> > drives but I worry that doing so will cause my duplicate 
> jobs to take longer as well
> > as hamper restore performance.  Need I be worried about that?
> 
> If you don't multiplex, then your max speed for the tape will be the
> max speed of the server yo are backing up.  If you factor in the
> compression ratio, you will have an even more difficult time
> maintaining the minimum sptreaming speed.
> 
> You almost certainly need to use multiplexing and cut down the number
> of active drives in your storage unit.   Try 1 drive and MPX=4.   If
> you can add a network link you should be able to add a second drive to
> your storage unit.
> 
> Austin
>