Correct, per Veritas support, this parameter is incapable of
auto-negotiating to the slowest/lowest drive.  (That would be a nice
feature to see in 5.0, hint)  

So if you have a media server that sees a mix of drives, say DLT 7000,
8000 and LTOs, then set it to 64K.  Otherwise, your restores "may" have
problems.  This is what they said.  i.e., trying to set the value too
high for an older tape may invalidate backups.  They suggested
increasing the SIZE_DATA_BUFFERS (buffer that writes to tape) to 256K
only on media servers that see only LTO drives.  But on all servers you
can bump up the NET_BUFFER_SZ (buffer that reads backup data from
network/client).  

-----Original Message-----
From: veritas-bu-admin AT mailman.eng.auburn DOT edu
[mailto:veritas-bu-admin AT mailman.eng.auburn DOT edu] On Behalf Of David Rock
Sent: Wednesday, December 17, 2003 9:54 PM
To: veritas-bu AT mailman.eng.auburn DOT edu
Subject: Re: [Veritas-bu] bptm logs

* Kohli, Vidit <vidit.kohli AT csfb DOT com> [2003-12-17 20:12]:
> 
> Guys
> 
> As far I experianced  NET_BUFFER_SZ will be always max 65536 depending
on the
> O/S
> 
> even you set 256K it won't exceed systems setup which is 65536

All the Solaris systems I have at work are correctly using the
NET_BUFFER_SZ that we havee set to 256K. What I have found equally
difficult is verifying what your drives' buffers are set to. You would
think a spec sheet for the drive would tell you...

Also, one more thing to think about. If you are using mixed-media (DLT
and 9940, for example) you want to make sure that the values you use are
the maximum for the LOWEST buffer size, or you may cause issues for the
lower system. Remember, this is a global setting on the media server
that will affect ALL drives connected to it.

-- 
David Rock
david AT graniteweb DOT com