Single-pass restore after a media failure

Abstract

When persistent storage fails, traditional media recovery first restores an old backup image followed by replaying the recovery log since the last backup operation. Restoring a backup can take hours, but log replay often takes much longer due to its random access pattern. We introduce single-pass restore, a technique in which restoration of all backups and log replay are performed in a single operation. This allows hiding log replay within the initial restore of the backup, thus substantially reducing the time and cost of media recovery and, incidentally, rendering incremental backup techniques unnecessary. Single-pass restore is enabled by a new organization of the log archive, created by a continuous process that is easily incorporated into the traditional log archiving process. Our empirical analysis shows that the imposed overhead is negligible in comparison with the substantial benefits provided.