On 11/05/15 15:55, Quinn Comendant wrote: > The process took about 8 hours, with fairly intense CPU usage and disk IO. Is > this dry-run considered representative for a typical backup session? In other > words, will tarsnap take 8 hours (discounting the time to actually do the > uploading) to discover what files need to be backed-up, every time? If so, my > plan to run it hourly is hopeless.
On subsequent runs tarsnap can recognize unmodified files and short-circuit the deduplication process. > The printed results show "new data, compressed size" is "245 GB". Is that > value before or after the magical de-duplication that is to be expected? > Will my monthly fee (at least initially) be approximately 245 * $0.25 = > $60/month? It looks like your 270 GB was deduplicated to 262 GB, which was then compressed down to 245 GB. > When I read that it’s “possible to store ‘archives adding up to several > terabytes’ while paying less than $10/month” I initially assumed the > deduplication compares my data with that uploaded by someone else (so my > "Rembihnútur.mp3" isn't uploaded, if another tarsnap user has already > uploaded "Rembihnútur.mp3"). But that’s not possible, because > deduplication is only per-account-key. Correct. The "adding up to several terabytes" is because you can have a large number of backups which deduplicate against each other -- for example I'm backing up about 50 GB of data from my laptop every hour, but I have about 20,000 archives; my 1.1 PB of data deduplicates down to 400 GB. > Then I assume my pricing estimate > above is accurate, and tarsnap is a high-end service that is not priced for > consumer use. =( I think most consumers only use tarsnap to back up their more important files, not the contents of their MP3 collections. ;-) Colin Percival > ------------------- > > [quinn@macbook] tarsnap --dry-run --print-stats --humanize-numbers -c > --exclude=Films /Users/quinn > tarsnap: Performing dry-run archival without keys > (sizes may be slightly inaccurate) > tarsnap: Removing leading '/' from member names > tarsnap: SystemKey: could not open file: Permission denied > Total size Compressed size > All archives 270 GB 251 GB > (unique data) 262 GB 245 GB > This archive 270 GB 251 GB > New data 262 GB 245 GB > tarsnap: Error exit delayed from previous errors. > -- Colin Percival Security Officer Emeritus, FreeBSD | The power to serve Founder, Tarsnap | www.tarsnap.com | Online backups for the truly paranoid
