>
> Bruce Elrick had an explanation of my problem (appended below) which
> sounds very convincing.  It perfectly describes what I saw.  I will
> check out the details later on this week.
>
> His explanation brings up another question, tho:
>
> If  I have multiple ADSM client sessions (be they buta or ordinary
> clients) which are in a management class where the disk storage pool is
> in readonly access mode (to force the data to go directly to tape), will
> I have a different tape mounted (and tape drive in use) for each session
> taking place simultaneously?

Yes. Maybe more, when various stgpools for some nodes are used
(mountretention).

>
> Otherwise, with the disk storage pool in readwrite mode, if I understand
> Bruce's explanation, it's a question of the relative rate of input to
> the disk (from the clients) and the output from the disk to tape by the
> migration processes.  E.g., if each of 4 client  inputs at 1-2 MB/sec
> and a migration process can write a tape at 4-5 MB/sec, then 2 migration
> processes should be sufficient to keep disk space available to the
> clients (with appropriately chosen lo and hi migration thresholds).
>

The migraion process needs some additional time for administrative
purposes. This relation depends on adsm object sizes (large objects -
low overhead) and, the backup has higher priority concerning mount
processes than migration has. This is important if you have as much or
more backup sessions as you have tape drives. I am working with lower
thresholds to make adsm start migration soon. (5/40 pct)

> Did I get that right?
>
> Thanks in advance.   John
>
> -----

Regards

Roger Hohmann

WestLB, ADSM Support, Herzogstra_e 15, D-40217 Duesseldorf
Tel.: +49211 826 8155, mailto:roger_hohmann AT westlb DOT de