Verify Volume Data Integrity

Verifying the data written to a Volume is done using a level = data for a Verify Job of Bacula. Such a Job will read all data records from a Volume, and for each object encountered, will calculate the checksum and record the size. That information is then compared against the metadata as stored on the Volume. Doing so, the Storage Daemon is able to detect data corruption on the storage media.

These Verify Jobs do not compare the data against what is stored in the Catalog, but it does read all job-related data from the storage media, passes them to the Storage daemon, and does the checksum processing, so they can be an integral part of ensuring reliability of the whole stack of interfaces and hardware involved.

Data level Verify Jobs are most useful with less reliable storage media, for example traditional file systems which do not provide redundancy, error correction, and “scrubbing” features. So-called “Next-Generation File Systems” like ZFS or btrfs, or highly reliable tape systems, are typically less prone to data corruption on media, so these Verify Jobs may be less important with them.