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From "Arthur Zubarev" <Arthur.Zuba...@Aol.com>
Subject Re: Dropped mutation messages
Date Wed, 19 Jun 2013 00:47:00 GMT
Cem hi,

as per http://wiki.apache.org/cassandra/FAQ#dropped_messages

Internode messages which are received by a node, but do not get not to be processed within
rpc_timeout are dropped rather than processed. As the coordinator node will no longer be waiting
for a response. If the Coordinator node does not receive Consistency Level responses before
the rpc_timeout it will return a TimedOutException to the client. If the coordinator receives
Consistency Level responses it will return success to the client.

For MUTATION messages this means that the mutation was not applied to all replicas it was
sent to. The inconsistency will be repaired by Read Repair or Anti Entropy Repair.

For READ messages this means a read request may not have completed.

Load shedding is part of the Cassandra architecture, if this is a persistent issue it is generally
a sign of an overloaded node or cluster.

By the way, I am on C* 1.2.4 too in dev mode, after having my node filled with 400 GB I started
getting RPC timeouts on large data retrievals, so in short, you may need to revise how you
query.

The queries need to be lightened 

/Arthur


From: cem 
Sent: Tuesday, June 18, 2013 1:12 PM
To: user@cassandra.apache.org 
Subject: Dropped mutation messages

Hi All, 

I have a cluster of 5 nodes with C* 1.2.4.

Each node has 4 disks 1 TB each.

I see  a lot of dropped messages after it stores 400 GB  per disk. (1.6 TB per node).

The recommendation was 500 GB max per node before 1.2.  Datastax says that we can store terabytes
of data per node with 1.2.
http://www.datastax.com/docs/1.2/cluster_architecture/cluster_planning

Do I need to enable anything to leverage from 1.2? Do you have any other advice?


What should be the path to investigate this?

Thanks in advance! 

Best Regards,
Cem.


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