incubator-cassandra-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Aaron Morton <aa...@thelastpickle.com>
Subject Re: Improving write performance in Cassandra and a few related issues...
Date Wed, 18 Dec 2013 02:59:33 GMT
> rite 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??? 
There is nothing in cassandra that would make that happen. Double check your client. 

>                                                            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??? 
What do you mean by packet drops ? 

Do you mean dropped messages in cassandra ? 

> 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?
Normally we expect 3k to 4k non counter writes per core per node, if you are not seeing that
it may be configuration or the client. 

Hope that helps. 
 
-----------------
Aaron Morton
New Zealand
@aaronmorton

Co-Founder & Principal Consultant
Apache Cassandra Consulting
http://www.thelastpickle.com

On 15/12/2013, at 7:51 pm, Krishna Chaitanya <bnsk1990rulz@gmail.com> wrote:

> Hello,
>        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?
> 
> Thanks.
> -- 
> Regards,
> BNSK.


Mime
View raw message