On Mon, Dec 05, 2011 at 01:51:05AM +0200, Timo Sirainen wrote: > I'm mainly wondering if it's common for backup programs to > support using a separate program to generate the backups. For > example if there was a "dovecot-backup" binary that just > dumps all (or new-since-last-backup) of the users' mails into > stdout, which the backup program can use. Or perhaps in that > case there wouldn't really be much of anything for the backup > to do except to write it to tape..
For databases, most commercial programs use some kind of application-specific plugins. Bakula has "Client Run Before Job" which permits indicating a command to be run before proceeding with the backup, maybe there is more. However I have not heard of any standardized way of doing it so that the application provider could provide a way to interact with multiple backup programs. It's more like each backup vendor boasting that his backup software can backup application XXX without downtime. > SIS was designed to work with hard links. They couldn't be > replaced with symlinks without a redesign (which would be less > efficient in normal operation). Right, but if the backup program recognized this then maybe the replacement by a symlink could be done only in the backup. rsync has to keep in memory all the inodes and check the list every time a hard link is found. If it knew that "a hard link in attachments should link to an identical file name in the common attachment SiS store. > [Zimbra] > > You mean you first create uncompressed zip files (why not > just tar?) of all the mails to the filesystem and the backup > software then backups those zip files? Well, not I, this is Zimbra's backup system :-) The backups are the destination zips. Maybe zip is used because the extension and extraction method is the same whether compressed or not; that way compression is just an option to the backup program to be turned on or off. > Dovecot's mdbox files already contain multiple messages in > each file, so it should be a lot more efficient to do backups > on those. And each message in an mdbox file can be compressed > if zlib plugin is enabled. So I think that sounds quite a lot > like what you propose. Is that combined or combinable with SiS? If attachments are in separate files, that means they are aligned on block boundaries, which make block-level SiS (like NetApp's) much more efficient. Think of an attachment sent to all department heads, all of whom forward the attachment to all their subordinates.
