What is EBS-backed instances and instance-store-backed instances.
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In Amazon Web Services (AWS), there are two main types of storage for Amazon Elastic Block Store (EBS) volumes associated with EC2 instances: EBS-backed instances and instance-store-backed instances.
EBS-Backed Instances:
EBS-backed instances are EC2 instances that use Amazon EBS volumes as their root devices. The root device is the primary storage device where the operating system and applications are installed. EBS-backed instances have the following characteristics:
Root Volume: The root volume of an EBS-backed instance is an Amazon EBS volume that persists independently of the instance's lifecycle. This allows for data retention even if the instance is stopped or terminated.
Data Persistence: EBS volumes attached to EBS-backed instances can be detached and reattached to other instances. This makes it easier to preserve and move data across instances.
Snapshot Capabilities: EBS volumes support snapshots, which are point-in-time copies of the volume. Snapshots can be used for backup, cloning volumes, and disaster recovery.
Elasticity: EBS-backed instances can be stopped and restarted, and their root volumes remain intact. This provides flexibility in managing instances while retaining data.
Instance-Store-Backed Instances (S3-Backed Instances):
Instance-store-backed instances, also known as S3-backed instances, use the instance store as their root device. The instance store is ephemeral, local storage physically attached to the host machine that is associated with the EC2 instance. Key characteristics include:
Ephemeral Storage: The data stored on the instance store is ephemeral, meaning it does not persist if the instance is stopped or terminated. The instance store is directly attached to the underlying hardware.
Performance: Instance-store-backed instances often provide better I/O performance compared to EBS-backed instances, especially for certain types of workloads.
Limited Persistence: If an instance-store-backed instance is stopped or terminated, any data on the instance store is lost. These instances are not designed for data persistence.
No EBS Snapshots: Since there is no EBS volume involved, there is no option to create EBS snapshots for backup and recovery.
Note: In recent instance types, AWS has been moving away from providing instance-store-backed instances, and many newer instance types only support EBS-backed instances.
When launching an EC2 instance, you can choose the root device type based on your requirements. EBS-backed instances are commonly used for data persistence, ease of management, and additional features such as snapshots. Instance-store-backed instances may be suitable for specific use cases that benefit from high-performance local storage but don't require data persistence beyond the instance's lifecycle.
