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 Replication latency

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ranvir_2k
Posting Yak Master

180 Posts

Posted - 2011-06-27 : 07:41:23
Hi all,

I'm facing an issue regarding replication latency.

I am replicating from a central server to two other nodes A and B.

The network latency between the central server and node B is 3 times the latency between the central server and node A.

However during heavy processing on the central server the replication latency on node B is 18 times that of on node A.

Is this exected behaviour? Or should replication latency on node B only be 3 times worse than node A?

nigelrivett
Master Smack Fu Yak Hacker

3385 Posts

Posted - 2011-06-27 : 07:44:54
It's queuing so the more traffic the longer the queue and the greater the latency difference.

Think of a traffic jam - the more the traffick the longer the queues and the longer it takes to move anywhere. Double the traffic - a lot more than double the time, especialy if it goes from no limiting queue.

Say you can handle 20 transactions a second - 1-20 transactions a second will have the same latency.
Another system that can handle 5 transactions a second will start queing at 6 tranactions a second and the difference between the two systems will rapidly up to 20 transactions a second. The difference ratio should still increase above 20 transactions a second but not by as much as the first system is now queueing also.

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ranvir_2k
Posting Yak Master

180 Posts

Posted - 2011-06-27 : 07:45:48
Yes this is what I thought.
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russell
Pyro-ma-ni-yak

5072 Posts

Posted - 2011-06-27 : 09:17:03
yeah, but why are you queuing? Are you seeing blocking on the subscriber? What is the disk queue length on the distributor and the subscriber?
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