EBS Multi-Attach: Attaching an EBS Volume to Multiple EC2 Instances

Overview

The Multi-Attach feature in Amazon Elastic Block Store (EBS) allows a single io1 or io2 volume to be attached to multiple EC2 instances within the same Availability Zone (AZ). This enables simultaneous read and write access across multiple instances, providing high availability for clustered applications.

Key Features of Multi-Attach

• Supports only io1 and io2 EBS volumes (does not work with gp3, gp2, or other volume types).
• Allows up to 16 EC2 instances to attach to the same volume simultaneously.
• Read and write permissions are granted to all attached instances.
• Restricted to a single Availability Zone (AZ)—the volume cannot be attached across multiple AZs.
• Requires a cluster-aware file system (not traditional XFS or EXT4).

Use Cases

• High-availability clustered applications (e.g., Teradata, Oracle RAC).
• Concurrent read/write operations that require multiple instances accessing the same dataset.
• Shared storage for applications running across multiple EC2 instances.

Limitations of Multi-Attach

1. Only supported on io1 and io2 volumes.
2. Cannot be used across different Availability Zones.
3. Supports a maximum of 16 EC2 instances per volume.