EBS Volume Types and Snapshots

EBS Volume Types

EBS provides following volume types: 

1. General Purpose SSD (gp2)

   • General purposes. Balances price and performance.

   • Ratio of 3 IOPS per GB upto 10,000 IOPS.

   • Burst upto 3000 IOPS for volumes under 1GB.

   • can store up to 16 TB

2. Provisioned IOPS SSD (io1)

   • For IO intensive. E.g. Large relational or NoSQL DBs.

   • For more than 10,000 IOPS.

   • Upto 20,000 IOPS per volume.

   • can store up to 16 TB

3. Throughput Optimized HDD (st1)

   • For big data, log processing etc. (sequential data)

   • Cannot be a boot volume.

4. Cold HDD (sc1)

   • For infrequently accessed. E.g. File server.

   • Lowest cost.

   • Cannot be a boot volume.

5. Magnetic (standard)

   • For infrequently accessed

   • Can be a boot volume

   • Lowest cost for boot volume capable.

EBS Snapshots

You can back up the data on your EBS volumes to Amazon S3 by taking point-in-time snapshots.

Snapshots are incremental backups, which means that only the blocks on the device that have changed after your most recent snapshot are saved. This minimizes the time required to create the snapshot and saves on storage costs. When you delete a snapshot, only the data unique to that snapshot is removed.

Important Notes on Snapshots:

1. You can change Volume types while creating a volume from a snapshot.

2. Can create a snapshot of an EBS volume through CLI as: aws ec2 create-snapshot.

3. Cannot delete a snapshot of an EBS Volume that is used as the root device of a registered AMI.

Additional Notes (Exam Tips)

1. While launching an instance instance store volumes are created from a template stored in Amazon S3 whereas, EBS volumes are created from Amazon EBS snapshots. This can lead to a slightly more time to launch instance store backed instances compared to EBS backed instances. 

2. You can attach additional EBS volumes even after launching an instance, but not instance store volumes.

3. In order to enable encryption at rest using EC2 and EBS you need to configure encryption while creating the EBS volume.

4. You can attach an EBS volume to an EC2 instance using AttachVolume API call.