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From Krishna Chaitanya <>
Subject Improving write performance in Cassandra and a few related issues...
Date Sun, 15 Dec 2013 06:51:15 GMT
       I am a newbie to the Cassandra world and have a few doubts which I
wanted to clarify. I am having a software switch that stores netflow
packets into a shared memory segment and a daemon that reads that memory
segment and stores them into a 2-node Cassandra cluster. Currently, I am
storing the packets from 2 hosts into 2 different keyspaces, hence only
writes and no reads. The write throughput is coming to around 460 pkts/sec
in each of the keyspaces. But, when I try to store the packets into the
same keyspace, I observe that the write throughput is remaining at around
460 pkts/sec or sometimes even falling below that rate as against the
expected rate of around 920 pkts/sec. Is it some kind of limitation of
Cassandra or am I doing something wrong???
                                                           I also see an
increase in packet drops when I try to store the packets from both the
hosts into the same keyspace. The packets are getting collected properly
followed by intervals in which they are being dropped in both the systems,
at the same time. Could this be some kind of a buffer issue???
                              The write requests from both the systems are
sent to the same node which is also the seed node. I am mostly using the
default Cassandra configuration with replication_factor set to 1 and
without durable_writes. The systems are i5s with 4 gb RAM. The data model
is: each second is the row key with all the packets collected in that
second as the columns. Also, can write throughput be increased by
distributing the write requests between the 2 Cassandra nodes instead of
sending the requests to a single node? Currently, I dont see any
improvement even  if I distribute the write requests to different hosts.
How can I improve the write performance overall?

*. *

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