Tarsnap GUI for the desktop
While we're discussing making Tarsnap more user-friendly:The single reason (other than, er, fecklessness on my part) why I haven't tried Tarsnap is that it seems difficult to predict how much using Tarsnap would actually cost me. I would need to know (1) how much space my data will take up after compression and deduplication, and (2) how much bandwidth my incremental backups will need -- again, after compression and deduplication.Wouldn't It Be Nice If there were a "predict my Tarsnap costs" tool? You download it and point it at your data. It compresses it and identifies duplicated blocks, and says "You would initially be storing about 25 GB of data on the Tarsnap servers, which will cost you about $6.70 per month." It records a bunch of hashes. Then, a little later, you run it again. It identifies changed blocks and compresses the differences (or something), and says "If you do an incremental update like this, you will transfer about 2GB of data, which will cost you about $0.54." With, each time, a disclaimer: "This is only a crude estimate and if you think Tarsnap, Inc., will be in any way bound by it then you're out of your mind."I'm not sure whether this is a thing that any random third-party person could write, or whether getting the numbers right would require information about exactly what happens on the Tarsnap servers that only Colin has. Perhaps the answer is that doing it right requires secret information, but doing it well enough (e.g., getting within 20%, 95% of the time) is easy with some naive algorithm like "divide everything into 4kB blocks, hash them all, identify duplicates, compress individual unique blocks with gzip; do the same for incremental updates but ignore blocks whose hash hasn't changed".I'm curious: is this a factor stopping other people signing up with Tarsnap? Is it perhaps only a factor for cheapskate individuals like me, and not for the larger organizations that probably represent most of Tarsnap's profits?