On Mon, Oct 16, 2000 at 01:36:16PM -0500, Andrew Steingruebl filled up my inbox 
with:
> 
> Ravi Channavajhala said:
> 
> >Is it possible to do network load balancing across several
> >physical interfaces in a media server i.e., one storage
> >unit being shared by several netbackup slave server
> >definitions eg., backup-e0, backup-e1, backup-e2?  The
> >primary definition is backup (nodename).  All these interfaces 
> >are on different subnets.  The storage unit is defined for
> >backup instance only.
> >
> >I already defined these in bp.conf on the master as well as
> >the slave.  What I dont understand is, how does the master
> >make a determination to direct a specific backup stream to
> >a specific network interface.  Thanks.
> >
> 
> There are 2 streams of traffic for each client.
> - backup stream
> - catalog stream
> 
> A server will automatically talk to another machine using the interface with 
> the best metric. On Unix, if you've got 2 interfaces, the system will use the 
> interface on the network its trying to reach.
> 

If only this were true for every platform. On Solaris, this is not the truth in 
practice. Also, if you have an environment like we have, with 11 interfaces 
trying to take 'least hop' to 30 changing VLAN's, you know that static routing 
is not a scalable solution, nor is 30 interfaces in a machine.

> The client will need to know about each server name.  So, what you probably 
> want to do is:
> 
> 1. Set up multiple "A" records/IP's for your master server.
> 2. Set up 1 storage unit and makes it owned by whatever interface name you 
> consider primary.
> 3. List all of the "aliases" for the master server in the bp.conf file on 
> master and slaves.
> 
> All backup traffic will take the optimal route. All catalog traffic must get 
> sent to "master" which is the top line in the bp.conf file.
> 
> You will have asymmetric traffic flows, but your backup data will tape the 
> optimal route.
> 

And if data goes up one interface, and down another for any reason (router 
failure, hsrp kicks in, different path is taken...), the software recovers less 
than gracefully. 'Chokes' is a better term.

With that said, it Does The Right thing(tm) most of the time, just not all of 
the time, and not as simply as stated.

-- 
"Any man page that includes the words "USE AT YOUR OWN RISK. BEWARE OF DOG. 
SLIPPERY WHEN WET" means trouble" - Michael Lucas
Joshua Fielden, Senior Systems Administrator and Backups Team Lead
eXcite@Home, Inc. jfielden AT excitecorp DOT com 650-556-3316