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From Michael Theroux <>
Subject Cassandra, AWS and EBS Optimized Instances/Provisioned IOPs
Date Wed, 12 Sep 2012 14:05:00 GMT

A number of weeks ago, Amazon announced the availability of EBS Optimized instances and Provisioned
IOPs for Amazon EC2.  Historically, I've read EBS is not recommended for Cassandra due to
the network contention that can quickly result (

Costs put aside, and assuming everything promoted by Amazon is accurate, with the existence
of provisioned IOPs, is EBS now a better option than before?  Taking the points against EBS
mentioned in the link above:

EBS volumes contend directly for network throughput with standard packets. This means that
EBS throughput is likely to fail if you saturate a network link.
According to Amazon, Provisioned IOPS guarantees to be within 10% of  of the provisioned performance
99.9%of the time.  This would mean that throughput should no longer fail.
EBS volumes have unreliable performance. I/O performance can be exceptionally slow, causing
the system to backload reads and writes until the entire cluster becomes unresponsive.
Same point as above.
Adding capacity by increasing the number of EBS volumes per host does not scale. You can easily
surpass the ability of the system to keep effective buffer caches and concurrently serve requests
for all of the data it is responsible for managing.
I believe this may be still true, although I'm not entirely sure why this is more true for
EBS volumes vs. emphemeral.

Any real world experience out there with these new EBS options?


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