I need some help understanding how ADSM uses tapes, especially when  there
is no available disk storage pool.

I've just started trying the use of the buta interface from AFS to ADSM.
I'm not sure my question is restricted to the use of buta, tho, so will
those who know about ADSM's use of tapes please keep reading.

Yesterday (yes, Sunday), I backed up about 35GB of disk via 4 buta ports (2
each on 2 stations).  All files went to a 4GB disk storage pool, with
reclamation set to hi/lo=60/30.  It worked, but I saw ADSM with up to 5
tapes mounted for the single migration process which lasted for the
duration
of the backup.  My feeling was that it wanted a tape for each buta
"stream",
if I may call it that.

So I restricted the tape device class to only one tape and started 2
streams
of backup.  One got its tape and went ahead to completion.  The other got
stuck.  I had to open the device class up to 2 tapes so it could mount a
second one, then the 2nd stream came to life.  But now, 10 minutes later,
both tapes are still mounted, and the tape dismount period is set to 2
minutes.

Can anybody help me to understand what's going on?

Thanks in advance.  John

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John O'Neall
John O'Neall
Centre de Calcul de l'IN2P3