A starting point for TSM data storage needs when moving from traditional backup 
methods can be calculated with these steps:
1. One full copy on tape
2. The amount of data backed up by one incremental backup multiplied by the 
greater of versions or the retention period.
3. multiply by 2 if you are using copy pools (everyone should IMHO)
 
This is just an estimate, the number of tapes needed will vary due to empty 
space.
 
In our case we have 3x the data on tape versus what is on the actual disks.  
Traditional backups had us at more than 9x.
 
 
 
Andy

________________________________

From: ADSM: Dist Stor Manager on behalf of Matthews, Gary
Sent: Thu 6/8/2006 5:00 AM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: [ADSM-L] Retention Query



 Hi,

Am a complete newbie when it  comes to TSM and have just been handed a
W2K3 system to look after with TSM 5.3. The system hasn't gone live yet
and I'm trying to work out how many tapes I'm going to need for
offsiting. We have four pools for onsite with the following setup


Vers Data  exits                28
Retain extra(days)      31
Vers Deleted            2
Retain Vers (days)      60

Do the copypools have the same characteristics?  If I'm sending four
tapes off a day how may tapes do I need for an offsite cycle ?? It's
just that the company that set things up have said that 30 LTO-3s should
be enough for onsite and offsite and I can't see how.

TIA

Gary (confused!)


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