"free space" is "shared" among all Gmail users. Major advantages Actively increasing storage efficiency using these techniques has the following advantages: Backup and restore. Using snapshots, time used for both backup and restore RTO can be minimized. This can greatly reduce cost, and reduce hours of downtime to seconds of downtime. Snapshots also allow for better RPO values. Reducing floorspace. When less storage is required to store a given amount of data, less data center floorspace is required. Reducing energy use. When fewer spindles are required to store a given amount of data, less power is required. Provisioning efficiency. Writable delta snapshot technology allows for very fast provisioning of writable data copies. This reduces waiting time in processes that require that data. Examples are data mining, test data, etc. Snapshot integration at the OS and/or application level also leads to faster provisioning, because system and/or application managers are able to manage their own snapshots without having to wait for storage managers and/or provisioning procedures. Major commercial players All major vendors are implementing one or more of these technologies, because storage efficiency is becoming more and more popular. Customers are facing storage requirements that are growing exponentially and a strong demand for cost-cutting. The major vendors are NetApp, EMC, HDS, IBM and HP. Computer data storage