On Thu, Mar 30, 2006 at 12:12:05PM -0500, Bob Stump wrote:
> A client is currently using 150GB as the threshold for determining
> whether a server should be a NetBackup media server or client.  This
> results in 30 SAN media servers using SSO and 730 clients that are
> multiplexed in about 70 policies.  The environment is the large STK
> SL8500 with 20 9940B tape drives

This is asinine.  We have about 150 clients and back up clients with
over 20TB of local storage.  We have 1 master and 2 media servers.  We
have NO SAN media servers.

> Please help me demonstrate the folly of this proposal.

> tape-drives will be shoeshining as the media servers will not be able
> to get the data to the drives fast enough

They should be able to if they stage to disk first.  For incrementals
that aren't staged, your performance will nose-dive instead of increase
since you will have 30 media servers but only 20 tape drives.  That
means that at least 10 of these media servers will be sitting around not
being able to do anything while another client that's doing a simple
incremental of 1 GB of changed data could tie up a tape drive for an
hour.

> license fees will be astronomical for SAN media servers

No doubt.

> tape drives will not be available when needed and jobs will fail with
> 134/196 errors

Jobs don't *fail* with a 134 but they will wait.  They will fail with
196s though.

> the number of tapes will increase since media servers do not share tapes

Yup.  

> The number of policies will cause bpsched to crunch continually

Nope.  You've only got 30 media servers so you don't necessarily have
*that* many policies.

> The catalog backup will never start or finish.

You can do hot catalog backups. You do require tape drives though and
you could run out of them if you're not careful.

> other reasons...please

We have seen cases where replacing a tape drive requires NetBackup to be
restarted on all of the media servers.  Other events also require a
NetBackup restart.  If those SAN media servers are Windows-based, this
means that you will need to reboot.

Note that 6.0 and 5.x media servers don't play well together (although
I've seen a report that this might be fixed in 6.0MP2).  This would mean
that you would have to upgrade *all* SAN media servers at the same time
as the master.  Again, if these are Windows, it ain't gonna be pretty.

There is a practical limit as to the number of media servers per master
server.  This is documented in the Tuning guide.

   .../Ed

-- 
Ed Wilts, Mounds View, MN, USA
mailto:ewilts AT ewilts DOT org