Typically, DRaaS requirements and expectations are documented in a service-level agreement (SLA) and the third-party vendor provides failover to a cloud computing environment, either through a contract or pay-per-use basis. In the event of an actual disaster, an offsite vendor will be less likely than the enterprise itself to suffer the direct and immediate effects, allowing the provider to implement the disaster recovery plan even in the event of the worst-case scenario: a total or near-total shutdown of the affected enterprise.
DRaaS can be especially useful for small to mid-size businesses that lack the necessary expertise to provision, configure and test an effective disaster recovery plan (DRP). Using DRaaS also means the organization doesn't have to invest in -- and maintain -- their own off-site DR environment. An additional benefit is that DRaaS contracts can be flexible as the business' needs change. The downside, of course, is that the business must trust that the DRaaS service provider can implement the plan in the event of a disaster and meet the defined recovery time and recovery point objectives.
Zetta.net, a cloud backup provider, adds cloud DRaaS