Resolution:
The engine daemon diagnostic messages in GridServer 6.1.1 log memory, disk and CPU status. For example:

"10/30 09:13:01:740 Info: [6.1.1.7] [OS: win64] [C: 2/0] [M: 8189M/3856M] [D: 98466M/?M)] [E: 277]"

Explanations follow:

[6.1.1.7]  is the Engine Daemon Version
[OS: win64] is OS Platform
[C: 2/0]  is the CPU Usage / Invoke Usage
[M: 8189M/3856M] is the amount of actual physical memory / the amount of physical memory currently available
[D: 98466M/?M)] is the free disk usage / total disk space (at the time of writing the total space is not read).
[E: 277] is the time in seconds since the last event.

Explanation of diagnostic messages in GridServer 6.1.1 engine daemon log.