On Wed, 8 Aug 2018, daniel_1983@protonmail.com wrote:
- rsync
may not be the best option depending on the format of mailboxes. If you're using maildir or maildir+ that's fine, but what about mbox or dbox ?
It depends on the situation. I can't speak for dbox, but if the mbox file is not updated, then it's no different than maildir. (It might actually be slightly faster as you don't read a lot of metadata for boxes with many messages. This is a consideration for Maildir if the filesystem format handles metadata poorly.)
For mbox where most of the updates occur at the end of the file (i.e. the latest messages), then you'll have to incur read I/O at the source to calculate rolling checksums, but only the changed blocks will be transferred.
The worst situation is a modification at the beginning of a large mbox (e.g. delete first message), which will trigger a full copy.
So for mostly static mboxes, and moderately sized active mailboxes, rsync will work fine, especially owing to its simplicity.
Joseph Tam <jtam.home@gmail.com>