Re: Replication factor - Consistency Questions

[Kirk True]

But isn't QUORUM on a 2-node cluster still 2 nodes?

On 07/17/2012 11:50 PM, Jason Tang wrote:

Yes, for ALL, it is not good for HA, and because we meet problem when use QUORAM, and current solution is switch Write:QUORAM / Read:QUORAM when got "UnavailableException" exception.

2012/7/18 Jay Parashar <jparas...@itscape.com <mailto:jparas...@itscape.com>>

    Thanks..but write ALL will fail for any downed nodes. I am
    thinking of QUORAM.

    *From:*Jason Tang [mailto:ares.t...@gmail.com
    <mailto:ares.t...@gmail.com>]
    *Sent:* Tuesday, July 17, 2012 8:24 PM
    *To:* user@cassandra.apache.org <mailto:user@cassandra.apache.org>
    *Subject:* Re: Replication factor - Consistency Questions

    Hi

    I am starting using Cassandra for not a long time, and also have
    problems in consistency.

    Here is some thinking.

    If you have Write:Any / Read:One, it will have consistency
    problem, and if you want to repair, check your schema, and check
    the parameter "Read repair chance: "

    http://wiki.apache.org/cassandra/StorageConfiguration

    And if you want to get consistency result, my suggestion is to
    have Write:ALL / Read:One, since for Cassandra, write is more
    faster then read.

    For performance impact, you need to test your traffic, and if your
    memory can not cache all your data, or your network is not fast
    enough, then yes, it will impact to write one more node.

    BRs

    2012/7/18 Jay Parashar <jparas...@itscape.com
    <mailto:jparas...@itscape.com>>

    Hello all,

    There is a lot of material on Replication factor and Consistency
    level but I
    am a little confused by what is happening on my setup. (Cassandra
    1.1.2). I
    would appreciate any answers.

    My Setup: A cluster of 2 nodes evenly balanced. My RF =2,
    Consistency Level;
    Write = ANY and Read = 1

    I know that my consistency is Weak but since my RF = 2, I thought
    data would
    be just duplicated in both the nodes but sometimes, querying does
    not give
    me the correct (or gives partial) results. In other times, it
    gives me the
    right results
    Is the Read Repair going on after the first query? But as RF = 2,
    data is
    duplicated then why the repair?
    Note: My query is done a while after the Writes so data should
    have been in
    both the nodes. Or is this not the case (flushing not happening etc)?

    I am thinking of making the Write as 1 and Read as QUORAM so R + W
    > RF (1 +
    2 > 2) to give strong consistency. Will that affect performance a lot
    (generally speaking)?

    Thanks in advance
    Regards

    Jay