Amazon's EBS backed AMI vs S3 backed AMI

Now that you are convinced, Amazon EC2 cloud is the way to go, which one will you choose EBS (Elastic Block Store) backed AMI or S3 (Simple Storage Service) backed AMI. Different factors that come into play in making the decision are listed below.

Factor	EBS backed AMI's	S3 backed AMI's
Storage Size	1TB	10GB
Instances can be stopped	Yes	No
Boot Time	Faster (~1min)	Slower (~5mins)
Local Instance Store	Not Available	Available
Data Persistence	EBS attached as volume (persist)	S3 is the root partition (doesn't persist)
AMI Creation	Easier and can be done using API	No API available for Linux
Charges	Volume Storage + storage usage + AMI Storage + Instance usage	AMI Storage + instance usage
Customized AMI Storage Charges	Lower (charged only for the changes)	higher (full storage charge)
Instance Usage Charge	No charge for stopped instances. Charge full instance hour for every transition from stopped to running state (.10 for full hour running, .30 for restarting twice in a hour)	Not Applicable

Amazon EC2 Limitations:

• 20 running instances
• Overall instance limit = 4xthe running instance limit
• 100 Amazon EBS Volumes or 20TB total volume storage
• 100 Security Groups