How to calculate disk space requirements when performing restores with System Recovery.

Problem

When performing restores with System Recovery, the following calculation can be used to understand the minimum disk space required for a successful restore.

Total size of the source volume divided by 16 + the total used space on the source volume.

Example:
Source volume total size = 60GB
Total used space on source volume = 20GB
Calculation: 60/16 = 3.75 + 20 = 23.75GB

Note: The pagefile size is also a consideration. If the source volume contains a pagefile, you should also allow a 'buffer' on the target disk to allow for this. A 4GB buffer is recommended (so above example would be 23.75 + 4 = 27.75GB).
 

Error Message

The following error may be seen if the target disk does not have enough space for the restore:

EC950006: Destination drive is not valid

Solution

Article provided as information only.