On 11/05/15 14:16, Quinn Comendant wrote: > Another question has come up while evaluating tarsnap. I'll be uploading > from a MacBook in rural Colombia, with a flapping internet connection. It > is a 3Mbps radio uplink, which is sufficiently fast to upload my 400GB > (pre-de-duplication) data in a month or two (initial upload), BUT the > connection is intermittent: the connection usually drops several times per > hour, and at worst every few minutes.
How long does it drop for? The tarsnap client will attempt to reconnect if its TCP connection drops; network outages of under 5 minutes shouldn't be a problem at all. If you use the --retry-forever option, it will do what you expect, too. > I've been reading about the > Interrupted Archives, and how subsequent archive creation (with a new > archive name) will resume a previously interrupted one. Not exactly *resume* -- but the new archive will be deduplicated against all past archives, including the partial one. > It seems this *might just work*, as long as I'm using a small > `checkpoint-bytes` value and an archive name with a timestamp, except that > every month I will have created maybe a few thousand archives. Perhaps > that's fine, if I never need to think about the archives on a human scale, > instead letting a script manage their creation and rotation. Obviously if I > will ever need to use the `--list-archives` or `--recover` commands this > would be insane. Nothing wrong with --recover. It just does something (check for an interrupted archive creation and finalize it into a partial archive) which gets done automatically the next time you create or delete an archive. > How would recoveries work, with so many archives? Let's say I discovered my > MacBook was compromised a week ago, and I want to do a full system > restoration to the state of the files uploaded 8 days ago. Would it be as > simple as running extract on the last archive with the timestamp of "8 days > ago", i.e., `tarsnap -x -f backup-YYYYMMDD.SSSSSSSSSSS /`, with the most > complete and consistent archive found by running something like `tarsnap > --list-archives | grep YYYYMMDD | sort | tail -1`? I'd go with something like `tarsnap --list-archives | fgrep -v .part | sort | tail -1` to get your most recent full archive. But you might not even need that; tarsnap is designed to work on internet connections which are not entirely reliable. -- Colin Percival Security Officer Emeritus, FreeBSD | The power to serve Founder, Tarsnap | www.tarsnap.com | Online backups for the truly paranoid
