Author: Michael Rogers Date: To: tech Subject: Re: [Tech] Distributed file system using routing inspired by Freenet
Matthew Toseland wrote: > We then multiply that by two from splitfile redundancy, to get a total
> redundancy of 6. Wuala works well with a factor of 5 redundancy... but that's
> entirely due to FEC.
Two FEC blocks each replicated three times aren't really comparable to
five FEC blocks, are they? You can't use any combination of them to
recover the data.
> They simulated ordinary redundancy and needed a factor
> of 24 to be reliable, but a factor of 5 for FEC.
I'm not convinced their churn model is realistic - they assume that the
nodes' uptimes are independent, but studies of Gnutella and Skype show
strong daily and weekly cycles - if each node is online 25% of the time
it doesn't follow that 25% of the nodes are online at any given time.
> So maybe what we need is less network level redundancy and more FEC level
> redundancy?
Sounds like a good idea, although won't it lead to higher search
overhead (each FEC block will be replicated fewer times)?
> Wuala's simulations assume 25% uptime, and they don't allow nodes to have
> extra storage unless they have at least 17% uptime. Can we implement
> something similar?
In theory we could reject inserts from peers that haven't been active
for, say, 4 of the last 24 hours, but in practice would that just drive
away users and decrease the amount of available content?
> A
> full blown reputation system as Wuala uses would be a lot of work and a lot
> of debugging...
Wuala has centralised identity management, Freenet doesn't. That means
we can't prevent Sybil attacks or whitewashing, which makes designing a
reputation system even harder. IMO it's a can of worms. Snakes, even.
Dragons!
