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FMS13, Backups, And Hardlinks

Question asked by ByteTheBullet on Nov 1, 2018

So, a silly question (I think)-

Using FMS13, and running a backup schedule. Configured to store 7 backups. If a database file does not change, FMS creates a hardlink to a previous backup in order to save time/space. What if the file doesn't change after 7 backups have run? How does FMS13 handle the backup in this case?


Backup 1: Full backup of file

Backup 2: hard link to backup 1

Backup 3: hard link to backup 1 (or is it backup 2?)

Backup 4: hard link to backup 1 (or is it backup 3?)

Backup 5: hard link to backup 1 (or is it backup 4?)

Backup 6: hard link to backup 1 (or is it backup 5?)

Backup 7: hard link to backup 1 (or is it backup 6?)

Backup 8: What happens to Backup 1? Schedule is set to keep only 7 backups, but only first backup is "real", while rest are hard links. Does FMS13 take Backup 1 and make it backup 2, regenerate all the hard links?


I would be surprised to discover that FMS13 would end up deleting backup 1, leaving a chain of nothing but hard links, but I can't find any documentation that explains just exactly what happens in a situation like this. FMS13 online help only states that a hard link is created if the file being backed up hasn't changed (assuming the file system supports hard links)- it's silent on what the process is for removing old backups and how that effects the remaining backups.