Memory usage for data and metadata as percentage (full eviction)

I conducted a small experiment with same sized buckets (100MB), with different sized documents and the same count of documents (3 million) then checked the memory usage. I have enabled full eviction and i took the average values of vb_active_itm_memory and vb_active_meta_data_memory as data and metadata respectively. The value was taken after 10000 random requests. My key is a 6 digit number.

I have few questions with the values I get.

  1. Why isn’t data+metadata add up to the same number
  2. for 651bytes collection i see the memory usage is 85 MB then how come data and metadata is only around 60MB ?


Thank you in advance