On 2019-06-03 at 12:47 +0100, Patrick O'Callaghan wrote: > On Mon, 2019-06-03 at 13:40 +0200, Ralf Mardorf via evolution-list > wrote: > > On Mon, 2019-06-03 at 12:06 +0100, Patrick O'Callaghan wrote: > > > Personally, I don't back up Evolution explicitly. I do back up my home > > > directory every night (using rsnapshot) but this almost always happens > > > while my session is logged in. I have been doing this for years and > > > have never lost an email. I probably also helps that my accounts are > > > IMAP-based, so what's in the local Evolution store is mostly cached > > > information. > > > > > > So it's not clear to me that stopping Evo during a backup is actually > > > necessary. > > > > Even if you would use POP accounts and Evolution would automatically > > download messages during the backup, it shouldn't matter. > > Yes, I would expect that. My question is whether all of Evo's database > operations are transactional, though I'm supposing they are. > > In which case I think the argument about how to make sure Evo is > stopped before doing a backup is pointless. Just don't stop it. > > poc
Even if a program is transactional, it only guarantees the state at a given point of time. Not that you can run a generic backup program in the background while the program works and that it will be consistent. In order to do that you would need to work on a frozen filesystem. For instance using LVM. btrfs also supports making a snapshot of a volume, which is atomic. Then you could run your backup program over that copy, and then (optionally) remove the snapshot. Suppose you were working locally on a maildir while you are running tar(1) for making a backup.¹ 1- tar reads the list of files on cur/ and starts reading them one by one to store them 2- you read a message, it gets renamed from 1528146778.123_0.evolution:2, to 1528146778.123_0.evolution:2,S 3- tar attempts to backup ‘1559682696.123_0.evolution:2,’, but as it's not there, will log an error and continue. The file has been on your mailbox for a year. The rename itself is atomic. A power failure would not lose that file [if it's on a journaled fs]. Yet your backup missed it. Kind regards ¹ This is a general race condition, most other programs would have the same problem. _______________________________________________ evolution-list mailing list evolution-list@gnome.org To change your list options or unsubscribe, visit ... https://mail.gnome.org/mailman/listinfo/evolution-list
