Logical vs. physical file system backup

Abstract

As file systems grow in size, ensuring that data is safely stored becomes more and more difficult. Historically, file system backup strategies have focused on logical backup where files are written in their entirety to the backup media. An alternative is physical backup where the disk blocks that make up the file system are written to the backup media. This paper compares logical and physical backup strategies in large file systems. We discuss the advantages and disadvantages of the two approaches, and conclude by showing that while both can achieve good performance, physical backup and restore can achieve much higher throughput while consuming less CPU. In addition, physical backup and restore is much more capable of scaling its performance as more devices are added to a system.