Tapes Estimated Capacity

[nabildz]

I am confused when I query tapes volumes, I get different estimated values eventhough they all using same devclass

can someone clarify please

Many Thanks

 

[nezih]

all data types have their spesific compression rate... if you use lto4 tapes for your backup it has 800 gb native / 1.6 Tb compressed capacity. backing up some nodes with files has approximately 1/2 compression rate you'll get 1,600,000.0 estimated capacity. But if this nodes got some files already compressed (like jpg,mpg,mp3,avi etc.) you'll get 800,000.0 estimated capacity. Or if you some nodes with files has higher compression rates you'll get 3,000,000.0 approx estimated capacity...

 

[nabildz]

all data types have their spesific compression rate... if you use lto4 tapes for your backup it has 800 gb native / 1.6 Tb compressed capacity. backing up some nodes with files has approximately 1/2 compression rate you'll get 1,600,000.0 estimated capacity. But if this nodes got some files already compressed (like jpg,mpg,mp3,avi etc.) you'll get 800,000.0 estimated capacity. Or if you some nodes with files has higher compression rates you'll get 3,000,000.0 approx estimated capacity...

thanks for clarifying this, so if I want to use MOVE DATA command to free up a tape to scratch, I need to look at PCT UTIL of the ESTIMATED CAPACITY and see if that size will fit on another tape from the same storage pool??

 

[BBB]

The real reason why you get different estimated values is actually this.

You set the estimate value for the device class yourself. You can set it to 10Mb or 10TB - but tsm will keep writing to a tape until its full no matter what you set as the estcap.

When a tape gets added to a stgpool it inherits the estimated capacity from the device class. Changing the device class will not change the est cap of any tapes that have already been put into stgpools, it will only affect new tapes.

At the moment a tape is full, tsm will then update the estimated capacity of that individual tape to the actual amount that had been stored onto to the tape.

 

[n9hmg]

If you're running into this as a problem because you're looking to figure out space for moving things around, you can get close with something like this:
bash-3.00$ runtsm "select VOLUME_NAME,integer(EST_CAPACITY_MB*PCT_UTILIZED/100) from VOLUMES where STGPOOL_NAME='LOCALTAPE'" |head -20
IBM Tivoli Storage Manager
Command Line Administrative Interface - Version 5, Release 5, Level 0.0
(c) Copyright by IBM Corporation and other(s) 1990, 2007. All Rights Reserved.

Session established with server TSM: AIX-RS/6000
Server Version 5, Release 4, Level 2.0
Server date/time: 12/01/08 13:35:20 Last access: 12/01/08 13:26:00

ANS8000I Server command: 'select VOLUME_NAME,integer(EST_CAPACITY_MB*PCT_UTILIZED/100) from VOLUMES where STGPOOL_NAME='LOCALTAPE''

VOLUME_NAME Unnamed[2]
------------------ -----------
TS0003L3 461857
TS0005L3 523001
TS0007L3 121196
TS0009L3 534421
TS0012L3 496945
TS0019L3 230799
TS0024L3 251280
TS0034L3 512159
bash-3.00$