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From Michael Theroux <>
Subject Re: VPC AWS
Date Thu, 05 Jun 2014 12:44:48 GMT
Hello Alain,

We switched from EC2 to VPC a couple of years ago.  The process for us was long, slow and
multi step.

In our case, we don't need to consider multi-DC.  However, in our infrastructure we were
rapidly running out of IP addresses, and wished to move to VPC to give us a nearly inexhaustible
supply.  In addition, AWS VPC gives us an additional layer of security for our Cassandra

To do this, we setup our VPC to have both private and public subnets.  Public subnets were
accessible to the Internet (when instances were assigned a public IP, while private subnets
could not (although instances on the subnet could access the Internet via a NAT instance).
 We wished for Cassandra on the private subnet. 

So, to achieve this, while still having an operating Cassandra DB without downtime, we essentially
had to stage Cassandra instances on our public subnet, assigning IPs and reconfiguring nodes
until we had a mixed EC2/VPC Public cluster, then start moving systems to the private subnet,
continuing the process until all instances were on a private subnet.  During the process
we carefully orchestrated configuration like broadcast and seeds to make sure the cluster
continued to function properly.  We also had to orchestrate the assigning of AWS security
groups to make sure everyone could talk to each other during this process.

Also keep in mind that the use of public IPs for communications will add to your AWS costs.
 During our transition we had to do this for a short time while EC2 instances were communicating
with VPC instances, but we were able to switch to 100% internal IPs when we completed (you
will still get inter availability zone charges regardless)

In order to make this successful, I created a script out

 From: Alain RODRIGUEZ <>
Sent: Thursday, June 5, 2014 8:12 AM
Subject: VPC AWS

Hi guys,

We are going to move from a cluster made of simple Amazon EC2 servers to a VPC cluster. We
are using Cassandra 1.2.11 and I have some questions regarding this switch and the Cassandra
configuration inside a VPC.

Actually I found no documentation on this topic, but I am quite sure that some people are
already using VPC. If you can point me to any documentation regarding VPC / Cassandra, it
would be very nice of you. We have only one DC for now, but we need to remain multi DC compatible,
since we will add DC very soon.

Else, I would like to know if I should keep using EC2MultiRegionSnitch or change the snitch
to anything else.

What about broadcast/listen ip, seeds...?

We currently use public ip as for broadcast address and for seeds. We use private ones for
listen address. Machines inside the VPC will only have private IP AFAIK. Should I keep using
a broadcast address ?

Is there any other incidence when switching to a VPC ?

Sorry if the topic was already discussed, I was unable to find any useful information...
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