Re: [Duplicity-talk] Duplicity Backup, volume size and reliability

[Kenneth Loafman]

Hi,

Sending to the mailing list as well.

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.

...Thanks,

...Ken

 

On Wed, Aug 16, 2017 at 6:00 AM, Huberius <address@hidden> wrote:

Hi,

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 corrupted?

The other question relates on reliability of incremental backup chains. Deja-Dup (which uses Duplicity) developers state on their wiki

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 risky.

[...]

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?

Regards,

Huberius