Each attached instance is able to drive its maximum IOPS performance up to the volume's maximum provisioned performance. However, the aggregate performance of all of the attached instances can't exceed the volume's maximum provisioned performance. If the attached instances' demand for IOPS is higher than the volume's Provisioned IOPS, the volume will not exceed its provisioned performance.
For example, say you create an io2 Multi-Attach enabled volume with
80,000 provisioned IOPS and you attach it to an m7g.large
instance that supports up to 40,000 IOPS, and an r7g.12xlarge
instance that supports up to 60,000 IOPS. Each instance can drive its
maximum IOPS as it is less than the volume's Provisioned IOPS of 80,000.
However, if both instances drive I/O to the volume simultaneously, their combined
IOPS can't exceed the volume's provisioned performance of 80,000 IOPS.
To achieve consistent performance, it is best practice to balance I/O driven from attached instances across the sectors of a Multi-Attach enabled volume.
For more information about IOPS performance for the Amazon EC2 instance types, see Amazon EBS optimized instance types in the Amazon EC2 User Guide.
