A team wants to attach a single EBS volume to multiple EC2 instances simultaneously for a clustered application using EBS Multi-Attach. Which statement about Multi-Attach is correct?
- Multi-Attach works with any EBS volume type, including gp3, as long as all instances are in the same Availability Zone
- Multi-Attach enabled io1/io2 volumes can be attached to up to 16 Nitro-based instances, but only within a single Availability Zone, and Multi-Attach does not by itself coordinate concurrent writes, so a standard file system like XFS or EXT4 still needs a cluster-aware layer on top
- Multi-Attach lets instances in different Availability Zones, and even different Regions, share the same volume for cross-Region high availability
- Multi-Attach can only be enabled at instance launch time via the RunInstances API, not afterward
Why B? And why not the others?
Correct answer: B. Multi-Attach enabled io1/io2 volumes can be attached to up to 16 Nitro-based instances, but only within a single Availability Zone, and Multi-Attach does not by itself coordinate concurrent writes, so a standard file system like XFS or EXT4 still needs a cluster-aware layer on top
EBS Multi-Attach is supported only on Provisioned IOPS SSD volumes (io1 and io2), and an enabled volume can be attached to up to 16 instances built on the Nitro System, but every attached instance must be in the same Availability Zone as the volume; Multi-Attach also doesn't provide its own write-ordering or locking, so ordinary file systems like XFS or EXT4, which assume only one server accesses them at a time, still need a cluster-aware file system layered on top to stay consistent under concurrent writes. The option claiming any volume type, including gp3, supports Multi-Attach is wrong because General Purpose SSD volumes don't support the feature at all. The option describing cross-AZ or cross-Region sharing is wrong because Multi-Attach is explicitly confined to a single Availability Zone; there's no mechanism for instances in different zones or Regions to share one Multi-Attach volume. The option restricting Multi-Attach to being enabled only via RunInstances at launch has it backwards: Multi-Attach specifically cannot be enabled during instance launch through the console or the RunInstances API, and must instead be enabled on the volume itself, separately from any single instance's launch.
Source: AWS EBS documentation: Attach an EBS volume to multiple EC2 instances using Multi-Attach — considerations and limitations