Veeam Backup Space Required: Formula and Calculation

By admin, October 31, 2010 12:03 pm

Found this really useful information in the Veeam’s forum (contributed by Anton), a great place to learn about the product and their staff are all very caring and warm.

The formulas we use for disk space estimation are the following:

Backup size = C * (F*Data + R*D*Data)
Replica size = Data + C*R*D*Data

Data = sum of processed VMs size (actually used, not provisioned)

C = average compression/dedupe ratio (depends on too many factors, compression and dedupe can be very high, but we use 50% – worst case)

F = number of full backups in retention policy (1, unless periodic fulls are enabled)

R = number of rollbacks according to retention policy (14 by default)

D = average amount of VM disk changes between cycles in percent (we use 10% right now, but will change it to 5% in v5 based on feedback… reportedly for most VMs it is just 1-2%, but active Exchange and SQL can be up to 10-20% due to transaction logs activity – so 5% seems to be good average)