4 ms·

Online backups for the truly paranoid

4 points by nodivbyzero 11y ago

cperciva 11y ago
I think most people here are already well aware of Tarsnap... but I'm always happy to answer questions.
- Cogito 11y ago
  For what it's worth: - I'm sure there are new people who have never heard of it before, I used to be one of them and your presence made it much more visible (that and everyone talking about how they trusted you to do crypto...) - I don't keep track of what's going on with tarsnap, so whenever it hits the front page I make sure to have a read and see if there is any new information So no question, just a thank you and a reminder to myself to set up my backups.
lwhalen 11y ago
How is this different from using Duplicity with a PGP key and throwing it to S3/B2?
- cperciva 11y ago
  That's a bit vague, but some of the more substantial differences are: 1. Duplicity works with a "full plus increments" model, whereas Tarsnap's archives are deduplicated snapshots. If you've been doing daily backups for a year, getting your data back using Duplicity means downloading a full backup followed by 365 increments; to get your data back using Tarsnap you directly download whichever archive you want. 2. Related to the above, Tarsnap's snapshot model allows you to delete archives independently; with Duplicity, you can't delete an archive if you want to keep increments which depend on it. 3. Tarsnap has built-in support for restricted keys; this allows you to set up a server which can create new archives but can't read or delete them. (With a bit of effort you can create "user" keys in AWS which can do S3 PUTs but not GETs or DELETEs; but if your server is compromised that wouldn't stop someone from overwriting your backups.) 4. Duplicity uses librsync, which is considerably more memory-hungry. It's possible that they worked around this by limiting its matching-block search to individual files -- I haven't looked at their code -- but that would result in it failing to recognize moved or copied files. 5. I haven't run benchmarks, but algorithmically speaking Tarsnap should be significantly faster at creating archives.
  - lwhalen 11y ago
    Thank you for the detailed reply!
rubinlinux 11y ago
For my nearly 1TB backup size, this would cost per month the same as my Crashplan account costs per year. Why are all these linux friendly backup services (this, rsync.net etc) so much more expensive?
- cperciva 11y ago
  Two reasons come to mind: 1. Tarsnap isn't VC-backed, so it can't play the "sell dollar bills for 80 cents each" game to expand its customer base. (On the flip side, this means that you don't have to worry about Tarsnap shutting down if it can't get any more VC money.) 2. "Consumer grade" backup services save a lot of money thanks to the fact that their customers skew heavily towards using only a small fraction of the storage space they are paying for. I think that approach to pricing is borderline dishonest; with Tarsnap you'll pay for exactly what you use (which means that a lot of people are paying a few cents per month).

4 points by nodivbyzero 11y ago

cperciva 11y ago

I think most people here are already well aware of Tarsnap... but I'm always happy to answer questions.

Cogito 11y ago
For what it's worth: - I'm sure there are new people who have never heard of it before, I used to be one of them and your presence made it much more visible (that and everyone talking about how they trusted you to do crypto...) - I don't keep track of what's going on with tarsnap, so whenever it hits the front page I make sure to have a read and see if there is any new information So no question, just a thank you and a reminder to myself to set up my backups.

lwhalen 11y ago

How is this different from using Duplicity with a PGP key and throwing it to S3/B2?

cperciva 11y ago
That's a bit vague, but some of the more substantial differences are: 1. Duplicity works with a "full plus increments" model, whereas Tarsnap's archives are deduplicated snapshots. If you've been doing daily backups for a year, getting your data back using Duplicity means downloading a full backup followed by 365 increments; to get your data back using Tarsnap you directly download whichever archive you want. 2. Related to the above, Tarsnap's snapshot model allows you to delete archives independently; with Duplicity, you can't delete an archive if you want to keep increments which depend on it. 3. Tarsnap has built-in support for restricted keys; this allows you to set up a server which can create new archives but can't read or delete them. (With a bit of effort you can create "user" keys in AWS which can do S3 PUTs but not GETs or DELETEs; but if your server is compromised that wouldn't stop someone from overwriting your backups.) 4. Duplicity uses librsync, which is considerably more memory-hungry. It's possible that they worked around this by limiting its matching-block search to individual files -- I haven't looked at their code -- but that would result in it failing to recognize moved or copied files. 5. I haven't run benchmarks, but algorithmically speaking Tarsnap should be significantly faster at creating archives.
- lwhalen 11y ago
  Thank you for the detailed reply!

rubinlinux 11y ago

For my nearly 1TB backup size, this would cost per month the same as my Crashplan account costs per year. Why are all these linux friendly backup services (this, rsync.net etc) so much more expensive?

cperciva 11y ago
Two reasons come to mind: 1. Tarsnap isn't VC-backed, so it can't play the "sell dollar bills for 80 cents each" game to expand its customer base. (On the flip side, this means that you don't have to worry about Tarsnap shutting down if it can't get any more VC money.) 2. "Consumer grade" backup services save a lot of money thanks to the fact that their customers skew heavily towards using only a small fraction of the storage space they are paying for. I think that approach to pricing is borderline dishonest; with Tarsnap you'll pay for exactly what you use (which means that a lot of people are paying a few cents per month).