On Tuesday 08 April 2008 21:09, Michael Rogers wrote: > 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.
Sure. It's not directly comparable. However, hopefully we have a higher average uptime, and the factor of 3 replication in the stores is necessary because of non-splitfile blocks. > > > 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. True. What would the impact of this be? > > > 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)? That may not be a bad thing, but just like on Wuala, we have requestor-side healing... > > > 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? Perhaps... I was thinking more in terms of storing stuff on nodes with reasonable uptimes... > > > 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! :) > > Cheers, > Michael -------------- next part -------------- A non-text attachment was scrubbed... Name: not available Type: application/pgp-signature Size: 189 bytes Desc: not available URL: <https://emu.freenetproject.org/pipermail/tech/attachments/20080408/b9dbb660/attachment.pgp>
