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From Yiming Sun <yiming....@gmail.com>
Subject Re: Cassandra read throughput with little/no caching.
Date Fri, 21 Dec 2012 14:36:01 GMT
I have a few questions for you, James,

1. how many nodes are in your Cassandra ring?
2. what is the replication factor?
3. when you say sequentially, what do you mean?  what Partitioner do you
use?
4. how many columns per row?  how much data per row?  per column?
5. what client library do you use to access Cassandra?  (Hector?).  Is your
client code single threaded?


On Fri, Dec 21, 2012 at 7:27 AM, James Masson <james.masson@opigram.com>wrote:

>
> Hi list-users,
>
> We have an application that has a relatively unusual access pattern in
> cassandra 1.1.6
>
> Essentially we read an entire multi hundred megabyte column family
> sequentially (little chance of a cassandra cache hit), perform some
> operations on the data, and write the data back to another column family in
> the same keyspace.
>
> We do about 250 writes/sec and 100 reads/sec during this process. Write
> request latency is about 900 microsecs, read request latency is about 4000
> microsecs.
>
> * First Question: Do these numbers make sense?
>
> read-request latency seems a little high to me, cassandra hasn't had a
> chance to cache this data, but it's likely in the Linux disk cache, given
> the sizing of the node/data/jvm.
>
> thanks
>
> James M
>

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