A company uses an Amazon Elastic File System (Amazon EFS) file system to share files across many Linux Amazon EC2 instances. A SysOps administrator notices that the file system's PercentIOLimit…

Question

Options

• ACreate a new EFS file system that uses Max I/O performance mode.
• BCreate an EFS lifecycle policy to transition future files to the Infrequent Access (IA) storage class
• CModify the existing EFS file system and activate Max I/O performance mode.
• DModify the existing EFS file system and activate Provisioned Throughput mode.

• A
  75% (18)
• B
  17% (4)
• C
  4% (1)
• D
  4% (1)

Explanation

Option A is correct because PercentIOLimit specifically measures how close an EFS file system is to the IOPS ceiling of General Purpose performance mode - hitting 100% means that ceiling has been reached, and the fix is to move to Max I/O performance mode, which is designed for high-throughput, highly parallel workloads. Critically, EFS performance mode cannot be changed after a file system is created, so a new file system must be created with Max I/O enabled.

Why the distractors are wrong:

• C is tempting but incorrect - EFS performance mode is immutable post-creation; you cannot modify it in place.
• D (Provisioned Throughput) addresses throughput limits, not IOPS; the symptom here is PercentIOLimit, which is an I/O operations bottleneck, not a throughput bottleneck - and changing throughput mode wouldn't resolve it.
• B (Infrequent Access lifecycle policy) is a cost-optimization feature that moves cold files to cheaper storage; it has no effect on performance.

Memory tip: Associate PercentIOLimit = 100% with "I've outgrown General Purpose" - and since you can't edit performance mode, you must create new. Contrast this with Throughput mode (Bursting/Provisioned/Elastic), which can be changed on an existing file system.

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