Memory allocation in Couchbase

Hi guys.
When I reserve memory for node how it happened? I mean is all it memory really allocated by system?
Or maybe it used some OS mechanisms to reserve but not allocate?

And about per bucket quote, does it only some kind of watermark which Couchbase is checked to not exceed?
Or there are some memory allocations occurred,.,.

bucket and memory quota are limits you communicate to couchbase. memory allocation is complex as there are many parts to the system so you may see total memory consumer exceed the quota so under certain conditions it may make sense to leave more room to the OS. The exact guidance depend on the workload and features you use - number of XDCR or number of views you enable etc. Perry’s blog is a good place to start if you’d like to get a deep understanding of this:

thanks a lot for you answer.
Perry’s block is very useful, many thanks =)

The link that you provided is not opening and can you provide any other links this is new link to Perry’s posts