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From Dominic Williams <dwilli...@system7.co.uk>
Subject Re: Clock skew
Date Tue, 28 Jun 2011 17:31:05 GMT
Hi, yes you are correct, and this is a potential problem.

IMPORTANT: If you need to serialize writes from your application servers,
for example using distributed locking, then before releasing locks you must
sleep for a period equal to the maximum variance between the clocks on your
application server nodes.

I had a problem with the clocks on my nodes which led to all kinds of
problems. There is a slightly out of date post, which may not mentioned the
above point, on my experiences here
http://ria101.wordpress.com/2011/02/08/cassandra-the-importance-of-system-clocks-avoiding-oom-and-how-to-escape-oom-meltdown/

Hope this helps
Dominic

On 27 June 2011 23:03, A J <s5alye@gmail.com> wrote:

> During writes, the timestamp field in the column is the system-time of
> that node (correct me if that is not the case and the system-time of
> the co-ordinator is what gets applied to all the replicas).
> During reads, the latest write wins.
>
> What if there is a clock skew ? It could lead to a stale write
> over-riding the actual latest write, just because the clock of that
> node is ahead of the other node. Right ?
>

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