I/O metrics to serve rate data along with delta

There are a number of metrics that are I/O related, e.g. disk bytes written/read, switch link bytes sent/received, instance NIC packets sent/received. Currently these metrics are in the form of deltas, i.e., some byte counters with a start date. To graph these metrics in terms of Gbps or MB/s, user needs to do their own conversion on the client side which is an additional overhead and can be error prone. Some tools provide native rate functions to output rate data if there are enough data points for it to calculate the "derivative" (3 is usually the minimum). However, in our case, the counters can get reset very quickly and oftentimes you get only one data point for each start time. Having rate data available as raw metrics or an OxQL transformation option will be very handy.

No file, test, or entry point is identified in the issue. Start by locating how I/O counters and their start dates are represented, then review the available metric and OxQL transformation paths. Done means users can obtain rate data for the listed I/O metrics without relying on client-side conversion, while preserving delta data.