By now, just about everyone is familiar with cloud-based backup services. Whether you're using simple file-based software tools or more complex image-based appliances, these services ship your data into secure cloud storage where it can be accessed at a moment's notice.
If you encounter a minor disaster (such as corrupted data), you simply download the affected files to your premises and get back to business. If you have a more severe sitewide disaster, you might need to source replacements to your on-premise server gear before you can do the restore. In both cases, online backup is in many ways similar to a traditional tape backup rotation that includes offsite tape storage -- except without the hassle of tapes.
Disaster recover as a service, or DRaaS, takes this concept a step further. Instead of just storing backups offsite where they can be restored to your premises, DRaaS offerings are coupled with cloud-based computing horsepower so that you can fire up your environment in the cloud as virtual machines, not just restore its data. DRaaS offers both offsite backup and a cloud-based warm site.
However, like constructing your own warm site, the use of DRaaS requires a significant amount of planning and preparation to use effectively in an actual disaster -- often requiring substantial changes to your on-premises network infrastructure. All too often, prospective DRaaS customers are wooed into a false sense of security by the capability to restore and run in the cloud, only to find that in an actual disaster their cloud-recovered environment is almost impossible to use effectively.