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Comment by yread | Hacker News Reader

I don't get it. How does it work?

How big is the hard drive in there? Judging from the price, the disk inside can't be much bigger than 2TB. That means if I have 1 TB of data and all the other have 1TB of their own data, it can only "replicated" exactly once (unless there are dedicated "cloud" servers involved), Which means, if my device breaks all devices which received a portion of my data need to be online for me to restore the content.

How does the encryption work? Surely the AES key can't be stored on the device - if it breaks your data is lost. If it's stored in the cloud it's not any safer than cloud storage.

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Your argument is mostly valid, but it assumes a couple of premises that are likely to be false:

1. All (or even most) users fully utilize their entire 1 TB quota. In reality, the vast majority of users will probably not even use half of their quota. By the time that changes, hard drive technology is likely to have advanced, and they can start selling larger boxes. Then the cycle repeats.

2. The data on the drives is not compressible. While people certainly could store only compressed files, that's not very convenient, and the reality is that most people will have at least some portion of content that is readily compressible.

Just by exploiting those two facts, the network can probably work without any external cloud assistance. But the smart way to design it would be to also have traditional cloud storage as a fallback. And that would be safer than traditional cloud storage, while still saving money since the fallback would only be used in special circumstances.

also getting multiple levels of redundancy doesn't necessarily need 1 X redundancy_level physical storage. see: http://en.wikipedia.org/wiki/Erasure_code and http://en.wikipedia.org/wiki/RAID#Comparison

Does this work with encrypted data, though? Properly encrypted data is indistinguishable from random data...

yes, the concept of erasure codes just works with the raw bits. so it would work equally for encrypted/unencrypted data from the wikipedia page, it "transforms a message of k symbols into a longer message (code word) with n symbols such that the original message can be recovered from a subset of the n symbols"

Perhaps they encrypt your unique personal files, but share duplicates among all the users? In one tb, there must be a lot of common mp3s, movie files, etc.

Dropbox does this too. I think I read somewhere that they md5 your file and see if matches one already on the network, if so, they just replicate a 'link' to that file in your account.

That's why sometimes if you upload a movie you downloaded, it uploads in a matter of seconds.

I thought they changed that because someone found that if you added that hash to your Dropbox to your local Dropbox database/config, it would download the movie. And for a week or two, people were pirating movies this way.

Though I suppose Dropbox could still use the same deduplication while making it harder to link a file to your account.

I believe they broke that scheme using other methods, which I can't recall.

Edit: They changed how it works on the server side, without going into detail. It's discussed here: https://news.ycombinator.com/item?id=2483053

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