AWS Certified SysOps Administrator – Associate (legacy) — Question 506

A company is using AWS Storage Gateway to create block storage volumes and mount them as Internet Small Computer Systems Interface (iSCSI) devices from on-premises servers. As the Storage Gateway has taken on several new projects, some of the Development teams report that the performance of the iSCSI drives has degraded. When checking the Amazon CloudWatch metrics, a SysOps Administrator notices that the CacheHitPercent metric is below 60% and the
CachePercentUsed metric is above 90%.
What steps should the Administrator take to increase Storage Gateway performance?

Answer options

• A. Change the default block size for the Storage Gateway from 64 KB to 128 KB, 256 KB, or 512 KB to improve I/O performance.
• B. Create a larger disk for the cached volume. In the AWS Management Console, edit the local disks, then select the new disk as the cached volume.
• C. Ensure that the physical disks for the Storage Gateway are in a RAID 1 configuration to allow higher throughput.
• D. Take point-in-time snapshots of all the volumes in Storage Gateway, flush the cache completely, then restore the volumes from the clean snapshots.

Correct answer: B

Explanation

A high CachePercentUsed (above 90%) combined with a low CacheHitPercent (below 60%) indicates that the gateway's local cache is too small to handle the working dataset, forcing the gateway to fetch data from S3 and causing latency. Increasing the size of the local cache disk allows more frequently accessed data to be stored locally, which improves performance. Modifying block sizes, setting up RAID 1, or flushing the cache with snapshots will not resolve the underlying capacity issue of the cache.