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From Mohit Anchlia <mohitanch...@gmail.com>
Subject Re: Monitoring replication lag/latency in multi DC setup
Date Thu, 06 Sep 2012 03:33:20 GMT
As far as I know Cassandra doesn't use internal queueing mechanism specific
to replication. Cassandra sends the write the remote DC and after that it's
upto the tcp/ip stack to deal with buffering. If requests starts to timeout
Cassandra would use HH upto certain time. For longer outage you would have
to run repair.

Also look at tcp/ip tuning parameters that are helpful with your scenario:

http://kaivanov.blogspot.com/2010/09/linux-tcp-tuning.html

Run iperf and test the latency.

On Wed, Sep 5, 2012 at 8:22 PM, Venkat Rama <venkata.s.rama@gmail.com>wrote:

> Hi,
>
> We have multi DC Cassandra ring with 2 DCs setup.   We use LOCAL_QUORUM
> for writes and reads.  The network we have seen between the DC is sometimes
> flaky lasting few minutes to few 10 of minutes.
>
> I wanted to know what is the best way to measure/monitor either the lag or
> replication latency between the data centers.  Are there any metrics I can
> monitor to find the backlog of data that needs to be transferred?
>
> Thanks in advance.
>
> VR
>

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