When you restore an automatic back-up of your VPS, it will cause the VPS to be unreachable for a while. This is the case because the backup of your VPS has to be retrieved from the external backup server before the VPS can start again with this data.
Hoe long does the backup restore process take exactly?
This depends on the total amount of data that has to be restored on the VPS. The data of a completely new VPS V1 can be restored in minutes, but a VPS with a maximally expanded disk can take up to several hours. On average a restore will take 30 to 60 minutes before being completed.
In the control panel a 'progress bar' will also appear when restoring a back-up. This will show the progression on a regular interval, but it could be so (especially for smaller back-ups) that the percentages have rather large leaps.