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From Krishna Chaitanya <bnsk1990r...@gmail.com>
Subject Re: Improving write performance in Cassandra and a few related issues...
Date Wed, 18 Dec 2013 04:02:36 GMT
Thanks for the reply.  By packet drops I mean, the client is not able to
read the shared memory as fast as the software switch is writing into it..
      I doubt its the issue with the client but can you in particular
issues that could cause this type of scenario?
   Also, I would like to know if in general , distribution of write
requests to different Casaandra nodes instead of only to one, leads to
increased write performance in Cassandra.
   Is there any particular way in which write performance can be measured,
preferably from the client???
On Dec 18, 2013 8:30 AM, "Aaron Morton" <aaron@thelastpickle.com> wrote:

> 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
> *. *
>
>
>

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