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From Edward Capriolo <>
Subject Re: Data retrieval inconsistent
Date Thu, 10 Nov 2011 21:09:09 GMT
On Thu, Nov 10, 2011 at 3:27 PM, Subrahmanya Harve <> wrote:

> I am facing an issue in 0.8.7 cluster -
> - I have two clusters in two DCs (rather one cross dc cluster) and two
> keyspaces. But i have only configured one keyspace to replicate data to the
> other DC and the other keyspace to not replicate over to the other DC.
> Basically this is the way i ran the keyspace creation  -
>    create keyspace K1 with
> placement_strategy='org.apache.cassandra.locator.SimpleStrategy' and
> strategy_options = [{replication_factor:1}];
>    create keyspace K2 with
> placement_strategy='org.apache.cassandra.locator.NetworkTopologyStrategy'
> and strategy_options = [{DC1:2, DC2:2}];
> I had to do this because i expect that K1 will get a large volume of data
> and i do not want this wired over to the other DC.
> I am writing the data at CL=ONE and reading the data at CL=ONE. I am seeing
> an issue where sometimes i get the data and other times i do not see the
> data. Does anyone know what could be going on here?
> A second larger question is  - i am migrating from 0.7.4 to 0.8.7 , i can
> see that there are large changes in the yaml file, but a specific question
> i had was - how do i configure disk_access_mode like it used to be in
> 0.7.4?
> One observation i have made is that some nodes of the cross dc cluster are
> at different system times. This is something to fix but could this be why
> data is sometimes retrieved and other times not? Or is there some other
> thing to it?
> Would appreciate a quick response.

disk_access_mode is no longer required. Cassandra attempts to detect 64 bit
and set this correctly.

If your systems are not running NTP and as a result their clocks are not in
sync this can cause issues (with ttl columns). Your client machines must
have correct time as well.

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