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How to delete old data from file backup sets?

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Hi Folks,




I'm backing up to an external hard drive and would like to control the size of the backup set on that external hard drive. I'd like to accomplish this by having Retrospect delete snapshots and backed up data that is older than a certain criteria...say four weeks.




This way the file set would always contain backups for the past four weeks and wouldn't grow extraordinarily large or need to be deleted and recreated thus wiping out all snapshots and backups from that period.




It would be great if Retrospect could do this automatically...or via Applescript...but I'd be willing to do it manually once a week or so if I had to.




Thanks in advance,





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I do something like this on occasion, though it won't do exactly what you want, and it's not for the faint of heart.




Basically I periodically chop the end off of the backup data file, rebuild the catalog, and then do a backup. This actually gets rid of newer backups rather than older ones, but you end up with the newest data (and it reduces the size of the file.) If you know roughly how big the data file was at the time of the original backup you can get rid of most of the redundant backups.




Basically I run the backup data file through the Unix "split" utility, patch the file type and creator with a handy freeware utility so that the truncated file looks like a Retrospect file again, run the catalog repair function on it, and then back up to it. Ugly and manual, but it does the trick.




It'd be much nicer if you could simply go into Retrospect and delete whatever snapshots you wanted to delete and then compress the data file, of course.

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That's an interesting approach, but it seems to be asking for trouble at some point. Especially when dealing with something as important as your backups. The best solution would be to have this feature implemented in Retrospect. Especially now with large drives becoming so cheap that file backup sets make sense economically.




I'm thinking now of a solution using two backup file sets: A and B. I want to keep four weeks worth of backup data in a set so I'll stagger A and B by two weeks. i.e. start A on the first and B on the fifteenth. Then on the first of the next month I'll delete A and start over. On the fifteenth of the next month I'll delete B and start over. With this approach the most disk space I'll need is 1.5X where X is the size of a single backup set with four weeks' worth of data. And at the worst-case scenario, right after either A or B are recycled, I'll still have two weeks of data.




If I kept the two sets on a two-week stagger as above, but ran them out to six weeks before deleting and recreating them then I'd always have at least four weeks of data but the disk space requirements would grow to 2.5X.




It's just a pain. This really should be a feature in Retrospect!

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