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From Russell Bradberry <>
Subject Re: in AWS is it worth trying to talk to a server in the same zone as your client?
Date Wed, 12 Feb 2014 20:17:36 GMT
Not when using private IP addresses.  That pricing ONLY applies if you are using the public
interface or EIP/ENI.  If you use the private IP addresses there is no cost associated.

On February 12, 2014 at 3:13:58 PM, William Oberman ( wrote:

Same region, cross zone transfer is $0.01 / GB (see,
Data Transfer section).

On Wed, Feb 12, 2014 at 3:04 PM, Russell Bradberry <> wrote:
Cross zone data transfer does not cost any extra money. 

LOCAL_QUORUM = QUORUM if all 6 servers are located in the same logical datacenter.  

Ensure your clients are connecting to either the local IP or the AWS hostname that is a CNAME
to the local ip from within AWS.  If you connect to the public IP you will get charged for
outbound data transfer.

On February 12, 2014 at 2:58:07 PM, Yogi Nerella ( wrote:

Also, may be you need to check the read consistency to local_quorum, otherwise the servers
still try to read the data from all other data centers.

I can understand the latency, but I cant understand how it would save money?   The amount
of data transferred from the AWS server to the client should be same no matter where the client
is connected?

On Wed, Feb 12, 2014 at 10:33 AM, Andrey Ilinykh <> wrote:
yes, sure. Taking data from the same zone will reduce latency and save you some money.

On Wed, Feb 12, 2014 at 10:13 AM, Brian Tarbox <> wrote:
We're running a C* cluster with 6 servers spread across the four us-east1 zones.

We also spread our clients (hundreds of them) across the four zones.

Currently we give our clients a connection string listing all six servers and let C* do its

This is all working just fine...and we're paying a fair bit in AWS transfer costs.  There
is a suspicion that this transfer cost is driven by us passing data around between our C*
servers and clients.

Would there be any value to trying to get a client to talk to one of the C* servers in its
own zone?

I understand (at least partially!) about coordinator nodes and replication and know that no
matter which server is the coordinator for an operation replication may cause bits to get
transferred to/from servers in other zones.  Having said there a chance that trying
to encourage a client to initially contact a server in its own zone would help?

Thank you,

Brian Tarbox

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