How Tarsnap uses Amazon Web Services
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How Tarsnap uses Amazon Web Services
1–10 of 17 posts
Re: How Tarsnap uses Amazon Web Services
#2Great post! I don't understand the paragraph about the cost of the PUTs and GETs though. The saving you get by batching writes seems marginal. Can you give some numbers?
Re: How Tarsnap uses Amazon Web Services
#3Very interesting. Do you have an estimate of how tarsnap compares to rsync in terms of bandwidth in the typical case that only a few files have been modified?
Re: How Tarsnap uses Amazon Web Services
#4Great post! I don't understand the paragraph about the cost of the PUTs and GETs though. The saving you get by batching writes seems marginal. Can you give some numbers?
How exactly do you batch writes? Do you save 2 blobs in 1 file? Or some kind of keep-alive that Amazon counts as a single request?
Re: How Tarsnap uses Amazon Web Services
#5Very interesting. Do you have an estimate of how tarsnap compares to rsync in terms of bandwidth in the typical case that only a few files have been modified?
Tarsnap is more efficient than rsync in that case, because rsync has a significant index overhead (sending a list of files, and sending a list of blocks for each file) while the tarsnap client works locally to identify new data and only uploads the new bits.
Re: How Tarsnap uses Amazon Web Services
#6Great post! I don't understand the paragraph about the cost of the PUTs and GETs though. The saving you get by batching writes seems marginal. Can you give some numbers?
The average block size the tarsnap server sees is about 30 kB (the tarsnap client tries to produce blocks of 64 kB on average, but then it compresses them individually before sending them to the server). This means that for every GB uploaded, there are about 33 thousand blocks.
S3 PUTs cost $0.01 per thousand PUTs, so writing each of the blocks as an individual S3 object would cost $0.33 / GB for PUTs (plus the normal $0.10 / GB for bandwidth).
Re: How Tarsnap uses Amazon Web Services
#7Great post! I don't understand the paragraph about the cost of the PUTs and GETs though. The saving you get by batching writes seems marginal. Can you give some numbers?
How exactly do you batch writes? Do you save 2 blobs in 1 file? Or some kind of keep-alive that Amazon counts as a single request?
I aggregate blobs together (up to 4 MB at once) and store them to S3 as a single S3 object. The tarsnap server keeps track of which part of the object corresponds to which blob.
Re: How Tarsnap uses Amazon Web Services
#8Tarsnap is really wonderful. I've been using it for about a month now and it's really simple. From your perspective, you're simply creating tar archives. No fuss, no muss.
On the tarsnap side, it makes sure not to duplicate storage or bandwidth for duplicate parts. Anytime you want to get a specific backup back, you just reference it by name. You can list the available archives. It's all encrypted. Pricing is based on what you actually use (rather than being rounded) which makes it ideal for small things as you can pay fractions of a cent.
It's definitely something to look into.
Re: How Tarsnap uses Amazon Web Services
#9I'm just curious, do all the people using these kinds of paid services just have really tiny hard drives? To back up 1TB of data via this system would cost around $250 a month in storage and transfer charges, and that's assuming very good compression is happening. What am I missing? Or maybe I'm just not rich enough for $3,000 / year?
Or maybe you're just doing a subset of your data, in which case I don't see how snapshotting is such a big win. Nice to have, but not important in the least if you are just doing a small subset of your data. True, it saves a few pennies on transfer charges, but you could save that much by doing the upload to S3 yourself.
My other concern with this is that if the tarsnap server ever goes away, customers risk losing their data, since the server maintains the mapping of S3 objects to blobs. That's worrying. Assurances are not mechanisms.
Re: How Tarsnap uses Amazon Web Services
#10I'm just curious, do all the people using these kinds of paid services just have really tiny hard drives? To back up 1TB of data via this system would cost around $250 a month in storage and transfer charges, and that's assuming very good compression is happening. What am I missing? Or maybe I'm just not rich enough for $3,000 / year? Or maybe you're just doing a subset of your data, in which case I don't see how sna…
do all the people using these kinds of paid services just have really tiny hard drives
Some tarsnap users back up all of their data; others just back up a subset. I'm not sure why you say that snapshotting isn't important -- in addition to the savings in bandwidth and storage, it makes tarsnap much faster and more convenient.
if the tarsnap server ever goes away, customers risk losing their data, since the server maintains the mapping of S3 objects to blobs
If the tarsnap server dies, I can launch a replacement EC2 instance and regenerate the metadata (as described in the article). If you're concerned about the possibility of me going away... well, if I get hit by a bus the tarsnap server will keep running on its own for at least the immediate future, but I have to concede that at the moment tarsnap won't survive indefinitely without me.
But I do my best to make sure that I won't get hit by a bus. :-)