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From Krishna Sankar <>
Subject Re: Deployment on AWS
Date Mon, 05 Apr 2010 03:45:52 GMT
    AFAIK, AZ gives you infrastructure redundancy but not necessarily
geographical dispersion. Regions are meant for that (as well as other
    An interesting blog on this topic

On 4/4/10 Sun Apr 4, 10, "Dan Di Spaltro" <> wrote:

> A little off-topic, but is an availability zone in a separate physical
> datacenter?
> On Sat, Apr 3, 2010 at 5:08 PM, Benjamin Black <> wrote:
>> Right, you determine AZ by looking at the metadata.  us-east-1a is a
>> different AZ from us-east-1b.  You can't infer anything beyond that,
>> either with the AWS API or guesses about IP addressing.  My EC2 snitch
>> recipe builds a config file for the property snitch that treats AZs
>> like racks (just breaking apart the AZ name, nothing magical), and the
>> rest is the normal rack aware placement strategy.  I am sure folks
>> _could_ do interesting things on EC2 with extra code, but I don't see
>> extra code as required for these basic features.
>> b
>> On Sat, Apr 3, 2010 at 3:04 PM, Joe Stump <> wrote:
>>> On Apr 3, 2010, at 2:54 PM, Benjamin Black wrote:
>>>> I'm pretty familiar with EC2, hence the question.  I don't believe any
>>>> patches are required to do these things.  Regardless, as I noted in
>>>> that ticket, you definitely do NOT need AWS credentials to determine
>>>> your availability zone.  It is available through the metadata web
>>>> server for each instance as 'placement_availability_zone', avoiding
>>>> the need to speak the EC2 API or store credentials in the configs.
>>> Good point on the metadata web server. Though I'm unsure how Cassandra would
>>> know anything about those AZ's without using code that's aware of such
>>> things, such as the rack-aware strategy we made.
>>> Am I missing something further? I asked a friend on the EC2 networking team
>>> if you could determine AZ by IP address and he said, "No."
>>> --Joe

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