We're working on improving the performance of our Moodle 2.6 integration at the moment. We have MUC working with two Memcache servers at the moment, however we're seeing very low utilisation of the servers themselves. Each server is configured with 2gb allocated to Memcache directly, however while running a load test with over 400 concurrent users, phpMemcacheAdmin is telling us that only 54.8mb is being used.
Hit/Miss ratio is fine, 99.9%/0.1%, so what's being added to the cache is being used - it's just that not much is actually being added. Low number of connections from the application itself.
What sort of Memcache utilisation are other people seeing?