EBS Multi-Attach

• EBS Multi-Attach enables attaching a single Provisioned IOPS SSD (io1 or io2) volume to multiple instances that are in the same AZ.
• Multiple Multi-Attach enabled volumes can be attached to an instance or set of instances.
• Each instance to which the volume is attached has full read and write permission to the shared volume.
• Multi-Attach helps achieve higher application availability in clustered Linux applications that manage concurrent write operations.
• There are no additional charges for using Amazon EBS Multi-Attach. Standard Provisioned IOPS SSD (io1 and io2) volume charges apply.

io2 Block Express with Multi-Attach

• io2 Block Express volumes are recommended over io1 for Multi-Attach due to better performance, durability, and feature support.
• io2 Block Express provides up to 256,000 IOPS, 4,000 MB/s throughput, and 64 TiB capacity per volume.
• io2 Block Express offers 99.999% durability (100x higher than io1) and consistent sub-millisecond latency.
• io2 Block Express volumes are now available in all commercial and AWS GovCloud (US) Regions (expanded in 2025).
• Customers can upgrade from io1 to io2 Block Express without any downtime using the ModifyVolume API.
• io2 offers up to 4x IOPS and 4x throughput at the same storage price as io1, and up to 50% cheaper IOPS cost for volumes over 32,000 IOPS.

NVMe Reservations (I/O Fencing)

• Multi-Attach enabled io2 volumes support NVMe reservations, a set of industry-standard storage fencing protocols for data consistency.
• NVMe reservations enable control and coordination of access from multiple instances to a shared volume.
• NVMe reservations is enabled by default for all Multi-Attach enabled io2 volumes created after September 18, 2023.
• For existing io2 volumes created before September 18, 2023, NVMe reservations can be enabled by detaching all instances and then reattaching them.
• Multi-Attach enabled io1 volumes do not support I/O fencing.
• Supported NVMe Reservation commands:
  • Reservation Register – registers, unregisters, or replaces a reservation key to associate an instance with a volume.
  • Reservation Acquire – acquires a reservation (Write Exclusive, Exclusive Access, Registrants Only, All Registrants types).
  • Reservation Release – releases or clears a reservation held on a volume.
  • Reservation Report – describes the registration and reservation status of a volume.
• Supported operating systems for NVMe reservations:
  • Amazon Linux 2 and later
  • RHEL 8.3 and later
  • SUSE Linux Enterprise 12 SP3 and later
  • Windows Server 2016 and later (NVMe driver 1.5.0+)

EBS Multi-Attach Considerations & Limitations

• Multi-Attach is supported exclusively on Provisioned IOPS SSD volumes (io1 and io2).
• Multi-Attach enabled volumes can be attached to up to 16 instances built on the Nitro System that are in the same AZ.
• Linux instances support Multi-Attach enabled io1 and io2 volumes.
• Windows instances support Multi-Attach enabled io2 volumes only.
• Multi-Attach for io1 volumes is available in limited Regions only: US East (N. Virginia), US West (Oregon), and Asia Pacific (Seoul). Multi-Attach for io2 is available in all Regions that support io2.
• io1 volumes with Multi-Attach enabled are not supported with instances built on the Nitro System that support the Scalable Reliable Datagram (SRD) networking protocol only. Use io2 with these instance types.
• Standard file systems (XFS, EXT4) are not designed to be accessed simultaneously by multiple servers. Use a clustered file system (e.g., GFS2, OCFS2) to ensure data resiliency and reliability for production workloads.
• Multi-Attach enabled volumes can be attached to one block device mapping per instance.
• Multi-Attach enabled volumes are deleted on instance termination if the last attached instance is terminated and if that instance is configured to delete the volume on termination.
• Multi-Attach enabled volumes can’t be created as boot volumes.
• Multi-Attach can’t be enabled during instance launch using either the EC2 console or RunInstances API.
• Multi-Attach can’t be enabled or disabled while the volume is attached to an instance.
• Multi-Attach option is disabled by default.
• CloudWatch metrics for Multi-Attach volumes are aggregated across all attached instances. Individual instance metrics are not available.

Volume Modification Support

• io2 Multi-Attach volumes support modifying volume size and provisioned IOPS after creation.
• io2 Multi-Attach volumes support enabling/disabling Multi-Attach (only while the volume is detached from all instances).
• io1 Multi-Attach volumes do not support any modifications (size, IOPS, or Multi-Attach state) after creation.
• Volume type cannot be changed for either io1 or io2 Multi-Attach enabled volumes.

Use Cases

• Clustered Linux Applications – High availability for applications using clustered file systems like GFS2 or OCFS2.
• Windows Server Failover Clustering (WSFC) – io2 volumes with NVMe reservations support SQL Server Failover Cluster Instances (FCI) on Windows Server.
• Amazon EKS Shared Storage – Multi-Attach can share persistent storage across multiple workloads in different EKS clusters within the same AZ.
• Database High Availability – Enables faster node recovery for clustered databases (e.g., Teradata reported 95% reduction in node recovery time).

AWS Certification Exam Practice Questions

• Questions are collected from Internet and the answers are marked as per my knowledge and understanding (which might differ with yours).
• AWS services are updated everyday and both the answers and questions might be outdated soon, so research accordingly.
• AWS exam questions are not updated to keep up the pace with AWS updates, so even if the underlying feature has changed the question might not be updated
• Open to further feedback, discussion and correction.

1. A company runs a clustered database application on multiple EC2 instances within the same Availability Zone. The application requires shared block storage with low latency and high IOPS. The application manages concurrent write operations. Which EBS configuration meets these requirements?
   1. Use a gp3 volume and attach it to multiple instances using Multi-Attach
   2. Use an io2 volume with Multi-Attach enabled and a clustered file system
   3. Use an io1 volume without Multi-Attach and replicate data between instances
   4. Use an EFS file system mounted across all instances

   Answer: 2. Multi-Attach is only supported on Provisioned IOPS SSD volumes (io1/io2). io2 is recommended. A clustered file system is required for concurrent write access.

2. A company wants to deploy SQL Server Failover Cluster Instances on AWS with shared storage. The solution must provide I/O fencing to prevent data corruption. Which approach should be used?
   1. Use io1 volumes with Multi-Attach enabled
   2. Use io2 volumes with Multi-Attach and NVMe reservations
   3. Use gp3 volumes with Multi-Attach enabled
   4. Use EFS with Windows Server instances

   Answer: 2. io2 volumes with Multi-Attach support NVMe reservations for I/O fencing. io1 does not support I/O fencing. gp3 does not support Multi-Attach. EFS does not support Windows natively for this use case.
3. Which of the following statements about EBS Multi-Attach are correct? (Choose 3)
   1. Multi-Attach enabled volumes can be attached to instances across multiple AZs
   2. Multi-Attach enabled io2 volumes support NVMe reservations for I/O fencing
   3. Windows instances support Multi-Attach for io2 volumes only
   4. Multi-Attach enabled volumes can be used as boot volumes
   5. io2 Multi-Attach volumes support modification of size and IOPS after creation

   Answer: 2, 3, 5. Multi-Attach is limited to a single AZ. io2 supports NVMe reservations. Windows only supports io2 for Multi-Attach. Multi-Attach volumes cannot be boot volumes. io2 volumes support size and IOPS modifications.

4. A solutions architect needs to provide shared block storage for a containerized application running on Amazon EKS. Instances are in a single AZ and the application requires high IOPS with consistent low latency. Which storage solution is most appropriate?
   1. Amazon EFS with Provisioned Throughput mode
   2. Amazon FSx for Lustre
   3. EBS io2 Block Express with Multi-Attach via the EBS CSI driver
   4. Instance store volumes shared via NFS

   Answer: 3. EBS io2 Block Express with Multi-Attach provides high IOPS, low latency block storage that can be shared across instances in the same AZ. The EBS CSI driver supports Multi-Attach for EKS workloads.

References

• AWS EBS Multi-Attach Documentation
• NVMe Reservations with Multi-Attach
• EBS Provisioned IOPS SSD Volumes
• Deploy SQL Server Failover Cluster with EBS Multi-Attach