==> On Mon, 25 Apr 2005 11:08:04 -0400, Richard Rhodes <rrhodes AT 
FIRSTENERGYCORP DOT COM> said:


> I'm trying to tune our mount retension settings on our device classes.
> Currently, we have it set to 3 min for our 3590 drives.  I'm not finding
> much info on how to tell if our 3 min period is too long or too short.


You're probably not going to see behavior problems because of "bad" mount
retention settings except in relatively extreme cases. But for your questions:


> I'm not sure of is whether a mount satisfied by a already mounted tape even
> has a mount msg in the log????

I don't think so.

> I'm also not sure whether a tape always waits for the mount retension period
> to be dismounted, or, whether it can be immediately dismounted if there are
> pending mount requests for other volumes.

Absolutely, yes.


In general, you'd want to increase your mount retention if you find that
you're dismounting and re-mounting the same volume many times in succession,
for "no good reason".

"Good reasons" basically come down to needing that drive mount point for some
other tape.  Dismounting because you need the mountpoint is pretty much
reasonable. :)


You'd want to decrease your mount retention if you find all of:

+ You usually have the wrong thing mounted
+ You usually have had it sitting idle for "a long time" (locally defined)
+ You are sensitive to the additional mount delay occasioned by a dismount


Or, (as in my case) you're polling your 3494 for tape occupancy on a regular
basis, and you want to have things dismounted if they're not immediately in
use, otherwise your numbers go awry.



- Allen S. Rout