UI Notes
Paying close attention to the capacity and usage numbers presented in the UI may raise some questions, as the numbers will fail to "add up" to the actual amount of data written to the ECS instance. This is not a bug but rather a design decision. The explanation is as follows:
ECS uses a data boxcarting strategy called "chunking." Chunks are pre-allocated when ECS is first initialized. When user data is written into ECS, pre-allocated chunks are filled and ECS pre-allocates however many new chunks ECS "thinks" would be best for the future based on what it knows about the past.
Capacity statistics are calculated based on allocated and pre-allocated chunks at the time statistics are requested and don't exactly reflect the actual amount of user data stored within ECS. We do this because it is a performance-enhacing heuristic that is a "good enough" representation of capacities without having to churn through the whole system to figure out the actual user data capacity numbers.