FAQ:Which backup program for filesystems is better?
From The Open Source Backup Wiki (Amanda, MySQL Backup, BackupPC)
Both dump and gnutar have advantages as well as disadvantages.
Dump can backup filesystems that are unmounted. Dump does not change filesystem metadata when the filesystems are backed up. Using dump, the backup window is reduced. Generally, dumping filesystem is faster than any other backup method. The main disadvantage of dump is the backed up filesystem data might be corrupted. Dump does not provide filesystem consistent view. Dumping an active filesystem may result in a backup image that cannot be restored. Dump is also very filesystem specific: a dump from one OS cannot be restored on a different OS. For more information, see dump information. Dump supports backup of only complete filesystems. Finer granularity of filesystem backups is not possible.
GNUTAR allows backup of directories and has the ability to exclude some directories and files using regular expressions. The GNUTAR archive is also portable between different OSes. GNUTAR can be used to backup live filesystems. Active files are included in the backup and you get a warning if a file is changed while being read; it's up to you to decide if that is bad or not for a particular file. GNUTAR normally modifies the last access time of the files (using option --atime-preserve=system fix this issue). GNUTAR can back up ACLs or extended filesystem attributes since GNUTAR 1.27.
To avoid trouble with active filesystems, or modifying metadata like atime, an alternative is to use hardware snapshots or LVM snapshots. Use snapshot to create a copy of the filesystem and backup the copy using GNUTAR or DUMP program.
For MacOS X, the DUMP program cannot be used. It does not backup extended attributes (resource forks) for HFS+ filesystems. GNU tar, a fully capable version of which is included in versions 10.4 and higher, works better. See Installing Amanda on Mac OS X for more detail.