[tahoe-dev] detecting weak uploads and share rebalancing Re: Share rebalancing

Shawn Willden shawn at willden.org
Sun Oct 11 01:41:09 UTC 2009


On Saturday 10 October 2009 05:36:20 pm Zooko Wilcox-O'Hearn wrote:
> The patch that Kevan has written for #778 would cause weak uploads to
> fail, as you desire, without changing your FEC parameters.

It wouldn't change my FEC parameters?  I thought his patch would change the 
current parameters to mean servers instead of shares, so I would think that 
setting H and N larger than the number of servers in the grid would be a 
problem.  I have K = number_of_servers.

> However 
> the current version of his patch has a problem -- in certain unusual
> edge conditions it could cause a strong upload to fail.

I haven't followed the patch very closely.  I guess I should go read about it.  
A lot of the terminology in the description assumes knowledge of the code, 
though, so my perception is that it would take significant effort to 
understand.

> > In any case, the more important part of my question was how to fix
> > the present problem, rather than how to avoid it in the future :-)
>
> Ah, yes.  So the process you described sounds like it would work, to
> me, but for immutable files there is an easier way -- just copy the
> share files to other servers.  :-)

I could do that, but I'd really like to get the shares to the *right* servers, 
per the permuted list, to minimize the likelihood that the repairer ends up 
placing shares poorly if the file has to be repaired.

	Shawn.



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