Cloud backup, also known as online backup, is a strategy for backing up data that involves sending a copy of the data over a proprietary or public network to an off-site server. The server is usually hosted by a third-party service provider, who charges the backup customer a fee based on capacity, bandwidth or number of users. In the enterprise, the off-site server might be proprietary, but the chargeback method would be similar.
Online backup systems are typically built around a client software application that runs on a schedule determined by the level of service the customer has purchased. If the customer has contracted for daily backups, for instance, then the application collects, compresses, encrypts and transfers data to the service provider's servers every 24 hours. To reduce the amount of bandwidth consumed and the time it takes to transfer files, the service provider might only provide incremental backups after the initial full backup.
Third-party cloud backup has gained popularity with small offices and home users because of its convenience. Capital expenditures for additional hardware are not required and backups can be run dark, which means they can be run automatically without manual intervention.
In the enterprise, cloud backup services are primarily being used for archiving non-critical data only. Traditional backup is a better solution for critical data that requires a short recovery time objective (RTO) because there are physical limits for how much data can be moved in a given amount of time over a network. When a large amount of data needs to be recovered, it may need to be shipped on tape or some other portable storage media. (See: AWS import-export)
Russ Fellows, Senior Analyst with the Evaluator Group, has put together the following chart to illustrate when cloud backups should be considered as a viable option.
|Backup factor||Cloud storage||Traditional backup|
|Amount of data||Best when the total amount to protect is less than 100 GB per 1 Mb of network bandwidth. For example, 100 GB can be supported by a 1 Mb WAN connection (such as DSL)||For large amounts of data, or for environments with limited network connectivity, traditional backup techniques are more appropriate.|
|Rate of change||Best when the rate of change is less than 10% of the total data per month.||For data that changes frequently, traditional backup methods that use local disk and tape, with tape transport off-site are more appropriate|