Difference Between Amazon S3 and Amazon EBS

S3 (Simple Storage Service) and EBS (Elastic Block Store) are two file storage services provided by Amazon. The main difference between them is with what they can be used with. EBS is specifically meant for EC2 (Elastic Computing Cloud) instances and is not accessible unless mounted to one. On the other hand, S3 is not limited to EC2. The files within an S3 bucket can be retrieved using HTTP protocols and even with BitTorrent. Many sites use S3 to hold most of their files because of its accessibility to HTTP clients; web browsers for example.

As already stated above, you need some type of software in order to read or write information with S3. With EBS, a volume can be mounted on an EC2 instance and it would appear just like a hard disk partition. It can be formatted with any file system and files can be written or read by the EC2 instance just like it would to a hard drive.

When it comes to the total amount that you can store, S3 still has the upper hand. EBS has a standard limit of 20 volumes with each volume holding up to 1TB of data. With S3, the standard limit is at 100 buckets with each bucket having an unlimited data capacity. S3 users do not need to worry about filling a bucket and the only concern is having enough buckets for your needs.

A limitation of EBS is its inability to be used by multiple instances at once. Once it is mounted by an instance, no other instance can use it. S3 can have multiple images of its contents so it can be used by many at the same time. An interesting side-effect of this capability is something called ‘eventual consistency’. With EBS, data read or write occurs almost instantly. With S3, the changes are not written immediately so if you write something, it may not be the data that a read operation returns.

Summary:

1. EBS can only be used with EC2 instances while S3 can be used outside EC2
2. EBS appears as a mountable volume while the S3 requires software to read and write data
3. EBS can accommodate a smaller amount of data than S3
4. EBS can only be used by one EC2 instance at a time while S3 can be used by multiple instances
5. S3 typically experiences write delays while EBS does not