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From Ashish Tyagi <tyagi.i...@gmail.com>
Subject High loads only on one node in the cluster
Date Thu, 31 Oct 2013 18:12:17 GMT
We have a 9 node cluster. 6 nodes are in one data-center and 3 nodes in the
other. All machines are Amazon M1.XLarge configuration.

Datacenter: DC1
==========
Address         Rack        Status State   Load
Owns                Token


ip11  1b          Up     Normal  76.46 GB        16.67%
0
ip12  1b          Up     Normal  44.66 GB        16.67%
28356863910078205288614550619314017621
ip13  1c          Up     Normal  85.94 GB        16.67%
56713727820156410577229101238628035241
ip14  1c          Up     Normal  17.55 GB        16.67%
85070591730234615865843651857942052863
ip15  1d          Up     Normal  80.74 GB        16.67%
113427455640312821154458202477256070484
ip16  1d          Up     Normal  20.88 GB        16.67%
141784319550391026443072753096570088105

Datacenter: DC2
==========
Address         Rack        Status State   Load
Owns                Token

ip21  1a          Up     Normal  78.32 GB        0.00%
1001
ip22  1b          Up     Normal  71.23 GB        0.00%
56713727820156410577229101238628036241
ip23  1b          Up     Normal  53.49 GB        0.00%
113427455640312821154458202477256071484

Problem is that node with ip address: ip11 often has 5-10 times more load
than any other node. Most of the operations are on counters. The primary
column family (which receives most writes) has a replication factor of 2 in
DataCenter DC1 and also in DataCenter DC2. The traffic is write heavy
(reads are less than 10% of total requests). We are using size-tiered
compaction. Both writes and reads happen with a consistency factor of
LOCAL_QUORUM.

More information:

1. cassandra.yaml - http://pastebin.com/u344fA6z
2. Jmap heap when node under high loads - http://pastebin.com/ib3D0Pa
3. Nodetool tpstats - http://pastebin.com/s0AS7bGd
4. Cassandra-env.sh - http://pastebin.com/ubp4cGUx
5. GC log lines -  http://pastebin.com/Y0TKphsm

Am I doing anything wrong. Any pointers will be appreciated.

Thanks in advance,
Ashish

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