Finally, numbers other than picodollars and gigabyte months and unpredictable deduplication. This convinces me I don't want to store 4TB there at a huge cost($12,000 if it's really $300 a year for 100GB) compared to buying two 4TB drives (~€250 per 3-4 years) and placing them at a friend's with free bandwidth.

Don't get me wrong: managed, off-site encrypted backups are very attractive, and I might be willing to pay a premium, especially for software from a trusted person, but not the cost price hundredfold.

Tarsnap isn't intended to be used as one-time backup like that, and it's super expensive if used that way. It's very cheap when used to backup (almost) the same 4GB for 1000 days in a row, which is what a lot of people/businesses need for their backup solutions.

It's not one time, I'd be incrementally writing updates to the disks. With a raspberry pi or something, the power costs are near negligible.

Rough estimate here:

If you upload 4tb in a year, that's 333.33gb/month

So for tarsnap that equals

- $1k/year in data transfer charges (4000gb * $0.25 transfer charge * 12 months)

- $83/month per month of data (333gb * $0.25 storage cost/month)

- $6.4k/year for the first year ($83 * 78 cumulative months in a year)

So $7.4k for 12 months resulting in 4tb

If usage stays the same each year will add $12k to the incremental yearly cost

> that's 333.33gb/month

I have 4TB of data, which changes an unknown amount (probably around 20-50GB per month) and grows slightly (probably 5-15GB per month).

In any case, thanks for the calculation. Tarsnap is apparently not for the common person who wants to back up everything including their media.

That actually works out worse - $14K for the first year, $13K for the second year.

Add another $1k to that for data transfer (assuming you only upload that 4tb once)

That sort of backup is what AWS Glacier is for, is it not?

I guess, I haven't really looked at it yet. And I'd have to find my own software to encrypt it before uploading. Tarsnap's software is one of the major selling points, at least to me.

I hate to think the cost if you had to restore that data from glacier though.

How much do you save after dedublication? Tar-snap could be a lot cheaper if you do frequent backups or you often change little in huge files.

Backup tools like attic (which I use) include automatic deduplication. There are surely minor differences in implementation, but tarsnap isnt the only implementation of deduplicating backup.