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From Jeff Ferland <>
Subject Re: Reduced write performance when reading
Date Thu, 23 Jul 2015 23:03:05 GMT
My immediate guess: your transaction logs are on the same media as your sstables and your OS
prioritizes read requests.


> On Jul 23, 2015, at 2:51 PM, Soerian Lieve <> wrote:
> Hi,
> I am currently performing benchmarks on Cassandra. Independently from each other I am
seeing ~100k writes/sec and ~50k reads/sec. When I read and write at the same time, writing
drops down to ~1000 writes/sec and reading stays roughly the same.
> The heap used is the same as when only reading, as is the disk utilization. Replication
factor is 3, consistency level on both reads and writes is ONE. Using Cassandra 2.1.6. All
cassandra.yaml settings set up according to the Datastax guide. All nodes are running on SSDs.
> Any ideas what could cause this?
> Thanks,
> Soerian

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