Efficiently Storing Virtual Machine Backups

Physical level backups offer increased performance in terms of throughput and scalability as compared to logical backup models, while still maintaining logical consistency. As the trend toward virtualization grows, virtual machine backups (a form of physical backup) are even more important, while becoming easier to perform. The downside is that physical backup generally requires more storage, because of file system meta-data and unallocated blocks. Deduplication is becoming widely accepted and many believe that it will favor logical backup, but this has not been well studied and the relative cost of physical vs. logical on deduplicating storage is not known. In this paper, we take a data-driven approach using user data to quantify the storage costs and contributing factors of physical backups over numerous generations. Based on our analysis, we show how physical backups can be as storage efficient as logical backups, while also giving good backup performance.