incubator-cassandra-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Brandon Williams <>
Subject Re: Dynamic Snitch / Read Path Questions
Date Tue, 14 Dec 2010 01:29:15 GMT
On Mon, Dec 13, 2010 at 6:43 PM, Daniel Doubleday

> Oh - well but I see that the coordinator is actually using its own score
> for ordering. I was only concerned that dropped messages are ignored when
> calculating latencies but that seems to be the case for local or remote
> responses. And even than I guess you can assume that enough slow messages
> arrive to destroy the score.

That's odd, since it should only be tracking READ_RESPONSE messages... I'm
not sure how a node would send one to itself.

Maybe I misunderstand but that would not really lead to less load right. I
> don't think that inconsistency / read repairs are the problem which leads to
> high io load but the digest requests. Turning off read repair would also
> lead to inconsistent reads which invalidates the whole point of quorum reads
> (at least in 0.6. I think rr probability has no effect in strong reads in
> 0.7) . Again assuming I am not misinterpreting the code.

Ah, I see what you want to do: take a chance that you pick the two replicas
(at RF=3, at least) that should agree, and only send the last checksum
request if you lose (at the price of latency.)


View raw message