When estimating the amount of disk space required, you should know the following:
•Total size of VMs being backed up
•Frequency of backups
•Retention period for backups
•Will jobs use forward or reverse incremental
You must also make assumptions on compression and deduplication ratios, change rates, and other factors. The following figures are typical for most sites; however, it is important to understand your environment if there are exceptions:
•Compression and deduplication savings 2:1 or more; typical is 3:1 or better, but always be conservative when estimating required space.
•Typical change rate of 5% day; this can vary tremendously per server and some environments are much higher.
•Include additional space for one-off full backups, and so on.
Using the numbers above, you can estimate required disk space for any job. Besides, you should always give plenty of extra headroom for future growth, additional full backups, moving VMs, restoring VMs from tape, and so on.
With Veeam Backup Management Suite or Veeam Essentials, you can use the VM Change Rate Estimation report from the Infrastructure Assessment pack as a ballpark pre-deployment assessment of the potential amount of free space that should be available on the target repositories. This report is built using the number of VM virtual disk write operations supplied by vSphere.
It is also recommended that you periodically run the Capacity Planning for Backup Repositories report from the Veeam Backup & Replication Reports pack to analyze the amount of free space on backup repositories and estimate the projected date when the repository will run out of available storage capacity. The report provides recommendations on how to adjust the allocated storage resources in order to meet the future demand for backup storage. Furthermore, it calculates the amount of additional space that needs to be provisioned to accommodate the necessary restore points.
For more information on Veeam Backup Management Suite, please refer to its Evaluator's Guide at http://helpcenter.veeam.com/evaluation/vbms/