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From Maki Watanabe <watanabe.m...@gmail.com>
Subject Re: Inconsistent data issues when running nodetool move.
Date Sat, 14 May 2011 10:41:00 GMT
It depends on what you really use which CL for your operations.
Your RF is 2, so if you read/write with CL=ALL, your r/w will be
always consistent. If your read is CL=ONE, you have chance to read old
data anytime, decommission is not matter. CL=QUORUM on RF=2 is
semantically identical with CL=ALL.

maki

2011/5/13 Ryan Hadley <ryan@sgizmo.com>:
> Hi,
>
> I'm running Cassandra (0.7.4) on a 4 node ring.  It was a 3 node ring, but we ended
up expanding it to 4... So then I followed the many suggestions to rebalance the ring.  I
found a script that suggested I use:
>
> # ~/nodes_calc.py
> How many nodes are in your cluster? 4
> node 0: 0
> node 1: 42535295865117307932921825928971026432
> node 2: 85070591730234615865843651857942052864
> node 3: 127605887595351923798765477786913079296
>
> So I started to migrate each node to those tokens.
>
> I have my replication factor set to 2, so I guess I was expecting to be able to continue
to use this ring without issues.  But it seems that the node still accepts writes while it's
decommissioning?  I say this because if I interrupt the decommission by stopping Cassandra
and starting it again, it appears to run through several commit logs.  And as soon as it's
through with those commit logs, I no longer get consistency issues.
>
> The issue I'm seeing is that writes to this ring will succeed, but it's possible for
a subsequent read to return an older object.  For several minutes even.
>
> I'm not sure if I did something wrong... learning as I go here and this list archive
has been very useful.  But, is there anyway I can rebalance the node and get better consistency?
>
> Thanks,
> Ryan

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