4 Storefront servers, 2 each in separate availability zones( A & B). 
The IIS log files on the 2 servers in the availability zone B are considerably larger than the other two.

• Traffic shown in IIS logs looks to be standard StoreFront related traffic.
• Looking at samples of random seconds (to make it easier to analyze) there is no apparent errors.
• Almost all entries are code 200. When we look into traffic Load Balancing (in NetScaler) and StoreFronts 3 and 4 are receiver about double the traffic / connections which would explain the difference in size for the logs.
• Upgrading Storefront version to latest will resolve the issue

Problem Cause