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From Jason Tang <>
Subject Consistency Problem with Quorum consistencyLevel configuration
Date Mon, 25 Jun 2012 01:15:32 GMT

    I met the consistency problem when we have Quorum for both read and

    I use MultigetSubSliceQuery to query rows from super column limit size
100, and then read it, then delete it. And start another around.

    But I found, the row which should be delete by last query, it still
shown from next around query.

    And also form normal Column Family, I updated the value of one column
from status='FALSE' to status='TURE', and next time I query it, the status
still 'FALSE'.

    More detail:

   - It not happened not every time (1/10,000)
   - The time between two round query is around 500 ms (but we found two
   query which 2 seconds happened later then the first one, still have this
   consistency problem)
   - We use ntp as our cluster time synchronization solution.
   - We have 6 nodes, and replication factor is 3

    Some body say, Cassandra suppose to have such problem, because read may
not happen before write inside Cassandra. But for two seconds?! And if so,
it meaningless to have Quorum or other consistency level configuration.

   So first of all, is it the correct behavior of Cassandra, and if not,
what data we need to analyze for further investment.


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