Re: How can I calculate the real utilization of tape-volumes ???

Sabine...

Since tape drives with compression don't tell the OS or application what the
compression ratio is (and how could they for an entire tape if the tape was
mounted/dismount interspersed with other tape mounts), you can't get the 'real
utilization' from the amount of data stored (which is what ADSM can track).
Mind you, if your data has a predictable compression you can set the estimated
capacity of the device class to the appropriate value (that is why you are
allow to set it).  But then you could also do that in your head as well.

How about:
def scr estutil desc='Show estimated utilization of volumes given estimated
compression: %1 is compression factor, $2 is volume match string'
upd scr estutil 'select volume_name as "Volume", pct_util, (pct_util/$1) as
"Est. %Util." -' l=1
upd scr estutil 'from volumes -' l=2
upd scr estutil "where volume_name like(upper('%$2%')) and status='FILLING' "
l=3

run estutil 2.5 vol12
Volume    PCT_UTIL    Est. %Util.
------    --------    -----------
vol120        55.0        22.0
vol120        55.0        22.0
...

Caveat: I haven't tried this or check my off-the-cuff syntax...

It would be nice if the tape formats included known lengths that were hardware
sensable (I'm sure many do) and it would be nice if the drives could respond to
a SCSI query about physically how far down a tape they were (I've never heard
of this), because then you would have the 'real utilization' you are looking
for.

Say, maybe if someone from IBM SSD (I know the ADSMers are moving over to
Tivoli, but they must keep in contact) can convince themselves that a tape
drive that could actually allow the OS or application to request the physical
tape position (with some level of uncertainty)  might actually have a (albeit
small) competative advantage over the others.  I would imagine that the drive
microcode and device driver changes would not be that difficult to implement.

Comments?

Cheers...
Bruce

Sabine Rettenberger wrote:

> Hi all,
>
> i want to see the real-utilization of tape volumes.
>
> With this SELECT-Command I can display only the estimated capacity and the
> percent-utilization, but i want to calculate the real-utilization if a tape
> is in filling-status.
>
> select est_capacity_mb, volume_name, pct_utilized from volumes where
> stgpool_name='backuptape_copy' and status='FILLING' and access='OFFSITE'
>
> How can i do calculations within an select-command ???
>
> thanks for your help
>
> Sabine

--
Bruce Elrick, Ph.D.
Bruce Elrick, Ph.D.
mailto:belrick AT home DOT com
http://members.home.net/belrick/