DataWriteIOBytes jump after switching EFS Throughput mode from bursting to elastic

The jump in DataWriteIOBytes after switching from Bursting to Elastic throughput mode is likely related to how Amazon EFS measures and reports throughput metrics rather than an actual change in your application's behavior.

When you switch to Elastic throughput mode, the way throughput is calculated and reported changes. In Elastic throughput mode, you're billed for the amount of data transferred (reads and writes), which means the system may be more precisely measuring and reporting the actual throughput being used.

The PermittedThroughput metric represents the maximum allowed throughput for your file system, which is calculated differently based on the throughput mode:

• For Bursting throughput, it's a function of file system size and BurstCreditBalance
• For Elastic throughput, it reflects the maximum write throughput of the file system

When you switched to Elastic throughput, the PermittedThroughput value likely increased, which corresponds with the jump you observed in DataWriteIOBytes. This doesn't necessarily mean your application is writing more data - it's more likely that the measurement and reporting of the throughput has changed.

The CloudWatch metrics for throughput monitoring (including WriteIOBytes) represent the actual throughput on your file system, but the way these metrics are calculated and reported can vary based on the throughput mode. Since your application didn't change its operations, the most probable explanation is that the switch to Elastic throughput mode altered how the write operations are being measured and reported rather than changing the actual amount of data being written.
Sources
Using CloudWatch metrics for Amazon EFS - Amazon Elastic File System
Managing file system throughput - Amazon Elastic File System
Amazon Elastic File System (EFS) | Cloud File Storage | FAQs