In general, long incremental backup chains are not advised. An error in one of the incrementals can cause the chain to fail past that point. I would suggest monthly backups and weekly verify runs to make sure all is well.
I have couple questions of Duplicity I couldn't find an answer
from forums or mailing lists.
I got curious of why the default volume size (25 MB) of Duplicity
is set so low. I found only this
thread back from 2007 about volume size and it's relation to
memory usage. Would increasing volume size, for example to 300 MB,
decrease the reliability of backups - full or incremental - as I
have read that large files would be more vulnerable of becoming
The other question relates on reliability of incremental backup
chains. Deja-Dup (which uses Duplicity) developers state on their
Déjà Dup will occasionally make fresh full backups for you.
This takes up more space and more time, but offers the
following benefits: * Sometimes there are bugs. If a bug appeared in the
middle of a chain of a year of incremental backups, you would
lose 6 months of backups. Now, bugs aren't expected, but
better safe than sorry. The occasional full backup prevents
hideously long chains of incremental backups, which can be
Déjà Dup assumes that [...] safety of data is paramount.
Back when I was using Deja-Dup, it wanted to make a new full
backup once around every three months after daily incremental
updates. From a technical point of view, is there any rule of
thumb when one should make a new full backup instead of continuing
with incremental ones? I suppose the risk of incremental backups
is simply a corruption of single backup file, and therefore a
breakup of backup chain?