Number of tapes

[spacewalker]

Hi,

How can i calculate the number of tapes i need to buy when i know the amount data backed up during one night and the retention period.

I have to crate 1 primary pool and 2 copy pools, one copy pool is used for off-site vaulting.

Best regards.

 

[jthillo]

No simple answer

Not sure I can give you a formula but a few thoughts come to mind:


1. What kind of drives/tapes are you using, LTO1 will require more tapes then LTO4, for example.

2. Are you going to use Collocation? Have you broken out the storage requirements per group? Collocation will require more tapes.

3. What is the expected growth rate you need to cover between tape purchases? It may sound silly but we can only buy tapes once a year so we have to project what our backup size will be in addition to where it is currently.

We are getting an average of 229 gigs on a tape (LTO2), however we are in the process of implementing collocation so this average will probably drop a bit.