CASA on Amazon Web Services: Instances
http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/EC2_GetStarted.html.

Overview

An instance is effectively a single computer composed of an OS, processors, memory, base storage and optional additional data storage. Amazon has predefined over 40 instance types. These fall into classes defined roughly by processing power, which are further subdivided by total memory and base storage.

Instance Types

A list of all Linux instance types with thier number of "vCPU", GB RAM, and the type of storage utilized by the instance type: https://aws.amazon.com/ec2/pricing/. Note the "vCPU" is actually a hyperthread, so 2 "vCPU" equal one core, e.g. m4.xlarge has 2 cores. (These prices are for on-demand instances.)

Starting Instances

CASA requires >=4GB/core. Storage can be EBS. Because AWS has hyperthreading turned on, each "vCPU" is one hyperthread and therefore 2 vCPUs essentially equal 1 physical core. Some experimentation may be required to optimize the instance type if many instances are to be used. This can have a very significant impact on total run time and cost. The 4GB per physical core rule should be sufficient to get started.

Choosing a Payment Option: On-demand vs. Spot

https://aws.amazon.com/ec2/spot/pricing/

Choosing an on-demand instance (the default) guarantees you the use of that instance (barring hardware failure).

There is also a Spot Price market. The price of an instance fluctuates over time. Using the spot market requires a bid. If that bid exceeds the spot price, then the spot instance will continue to run. Typically the spot price is much less than the on-demand price, so bidding the on-demand price typically permits an instance to run its job to completion. And, during the time it runs, it is billed only at the running spot price, not the bid, so the savings can be considerable.

For example, the on-demand price for a m4.xlarge instance is $0.239/hour. For the past 3 months, the mean spot price has been $0.0341 (maximum $0.0515/hour). A 10-hour run of 100 instances would have cost $239 for on-demand and $34 for spot instances. That assumes adding 100 instances to the spot market will not affect the spot price much, which is a reasonable assumption. However, adding 500 instances will certainly raise the spot price.

It's possible to bid up to 10 times the on-demand price.

https://aws.amazon.com/ec2/purchasing-options/
There are other ways to purchase AWS instances, but only on-demand and spot instances appear of interest to running CASA.

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