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. > >> 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.
I have observed this first hand in a crawler I implemented long ago for the Shareaza network. See, for example, here: http://crawler.trillinux.org/history.html (I'm no longer maintaining these pages, BTW. Somebody took over circa 2005.)
