Operating system backup

The first thing to consider is the operating system. A typical scenario is to have controlled releases of service packs and Windows updates. Under this scenario you would not backup or restore Windows but reinstall to the appropriate patch and Windows update.

Strategies that use a complete system image for the backup are much harder to implement, test, and validate. Even with this strategy you still need database backups to handle non-disaster recovery (for which you do not lose the operating system) and to handle the differential or transaction log backups (which are required at a higher frequency than is reasonable from an image backup). For these reasons, in most situations, image backups are not recommended.