On Apr 8 2008, Matthew Toseland wrote:
>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.

In theory would it be possible to use FEC for all blocks, or is it wasteful 
if you have less than one segment's worth of data?

>> 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?

There would be fewer nodes online at certain points in the cycle (eg 4am on 
Monday morning) so you'd need higher redundancy (or at least a warning 
saying "No glot, clom Fliday").

>> > 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...

True, but I was thinking of the number of hops the search will have to 
travel: one block replicated three times can be found more cheaply than one 
of three blocks replicated once each. (Higher FEC redundancy is still a 
good idea IMO, I'm just thinking about the tradeoffs.)

>Perhaps... I was thinking more in terms of storing stuff on nodes with 
>reasonable uptimes...

Good point, I guess it's a waste of bandwidth to store data on a transient 
node.

Cheers,
Michael

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