Amazon Elastic Block Store

Block storage used as a disk for EC2.

Block storage attached to EC2. Used as OS or data disks.

• Root volume for EC2
• Disk for databases
• Backups via snapshots

• Block storage attached to EC2
• Backups are taken with snapshots
• Tied to an Availability Zone

• Choose volume type based on performance requirements
• Snapshots are stored in S3 but users do not access them directly
• Consider enabling encryption

Amazon EBS (Elastic Block Store) is a **block storage** service that is attached to an EC2 instance. From the OS perspective, it is recognized as an ordinary disk drive, and data can be read and written by mounting a file system on it. EBS volumes must be located in the same Availability Zone (AZ) as the EC2 instance, and **cannot be attached across AZs**. **The differences from object storage (S3) and file storage (EFS)** are frequently asked about. EBS is suited for high-speed I/O scenarios where it is attached to a single EC2 instance as a block device. S3 is accessed per object via HTTP API, so it cannot be used as a disk from EC2. EFS is a shared file system that can be mounted simultaneously from multiple EC2 instances. **Volume types** are selected according to the workload. General purpose SSD gp3 is the most common choice and offers good cost efficiency. Provisioned IOPS SSD io2 is used for database workloads that require high IOPS. Throughput-optimized HDD (st1) suits large-volume sequential read/write workloads (logs, big data processing), and Cold HDD (sc1) is a low-cost option for infrequently accessed large volumes of data. **Snapshots** are a feature that stores point-in-time copies of EBS volumes in S3. Users can perform the operation without being aware of the underlying S3 bucket. Snapshots use an incremental backup approach: after the initial full snapshot, only the changed differences are stored, making the process efficient. You can restore a new EBS volume from a snapshot or copy it to another region for DR purposes. An important note: **even if you stop the EC2 instance, the attached EBS volume continues to incur charges**. Unused volumes will continue to generate costs unless they are explicitly deleted. CLF-C02 asks questions such as "which storage is used as the disk for EC2?" and "which is a block storage tied to an AZ?". SAA-C03 asks about the criteria for selecting volume types, Multi-Attach (a limited feature of io1/io2), encryption (integration with KMS), and snapshot lifecycle management.

• Amazon EBS (AWS Official)
• What is Amazon EBS (AWS Official Documentation)
• Amazon EBS Volume Types (AWS Official Documentation)

Last updated: 2026-06-01