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From Russell Bradberry <>
Subject Re: EBS SSD <-> Cassandra ?
Date Thu, 19 Jun 2014 20:39:36 GMT
does an elastic network interface really use a different physical network interface? or is
it just to give the ability for multiple ip addresses?

On June 19, 2014 at 3:56:34 PM, Nate McCall ( wrote:

If someone really wanted to try this it, I recommend adding an Elastic Network Interface or
two for gossip and client/API traffic. This lets EBS and management traffic have the pre-configured

On Thu, Jun 19, 2014 at 6:54 AM, Benedict Elliott Smith <>
I would say this is worth benchmarking before jumping to conclusions. The network being a
bottleneck (or latency causing) for EBS is, to my knowledge, supposition, and instances can
be started with direct connections to EBS if this is a concern. The blog post below shows
that even without SSDs the EBS-optimised provisioned-IOPS instances show pretty consistent
latency numbers, although those latencies are higher than you would typically expect from
locally attached storage.

Note, I'm not endorsing the use of EBS. Cassandra is designed to scale up with number of nodes,
not with depth of nodes (as Ben mentions, saturating a single node's data capacity is pretty
easy these days. CPUs rapidly become the bottleneck as you try to go deep). However the argument
that EBS cannot provide consistent performance seems overly pessimistic, and should probably
be empirically determined for your use case.

On Thu, Jun 19, 2014 at 9:50 AM, Alain RODRIGUEZ <> wrote:
Ok, looks fair enough.

Thanks guys. I would be great to be able to add disks when amount of data raises and add nodes
when throughput increases... :)

2014-06-19 5:27 GMT+02:00 Ben Bromhead <>:

From the link:

EBS volumes are not recommended for Cassandra data volumes for the following reasons:

• 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.
• EBS volumes have unreliable performance. I/O performance can be exceptionally slow, causing
the system to back load reads and writes until the entire cluster becomes unresponsive.
• 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.

Still applies, especially the network contention and latency issues. 

Ben Bromhead
Instaclustr | | @instaclustr | +61 415 936 359

On 18 Jun 2014, at 7:18 pm, Daniel Chia <> wrote:

While they guarantee IOPS, they don't really make any guarantees about latency. Since EBS
goes over the network, there's so many things in the path of getting at your data, I would
be concerned with random latency spikes, unless proven otherwise.


On Wed, Jun 18, 2014 at 1:58 AM, Alain RODRIGUEZ <> wrote:
In this document it is said :

Provisioned IOPS (SSD) - Volumes of this type are ideal for the most demanding I/O intensive,
transactional workloads and large relational or NoSQL databases. This volume type provides
the most consistent performance and allows you to provision the exact level of performance
you need with the most predictable and consistent performance. With this type of volume you
provision exactly what you need, and pay for what you provision. Once again, you can achieve
up to 48,000 IOPS by connecting multiple volumes together using RAID.

2014-06-18 10:57 GMT+02:00 Alain RODRIGUEZ <>:


I just saw this :

Since the problem with EBS was the network, there is no chance that this hardware architecture
might be useful alongside Cassandra, right ?


Nate McCall
Austin, TX

Co-Founder & Sr. Technical Consultant
Apache Cassandra Consulting
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