Memory still seems to be the item that prompts most upgrades, with VM’s running
out of memory before running out of vCPU.
It’s not just a question of how much of it is being used as there are
different ways of monitoring it. Some of the things that you are going to need
to consider are:
– Reservations
– Limits
– Ballooning
– Shared Pages
– Active Memory
– Memory
Available for VMs
VM Memory
Occupancy
In terms of occupancy the sorts of things that you will want to look at
are:
–
Average Memory overhead
–
Average Memory used by the VM(active memory)
–
Average Memory shared
–
Average amount of host memory consumed by the VM
–
Average memory granted to the VM
In this instance we can see that the pink area is active memory and we
can note that the average amount of host memory used by this VM increases at
certain points in the chart.
VM Memory
Performance
It is useful to produce a performance graph for memory where you can
compare:
–
Average memory reclaimed
–
Average memory swapped
–
Memory limit
–
Memory reservation
–
Average amount of host memory consumed.
As illustrated below.
In this instance we can see that this particular VM had around 2.5gb of
memory ‘stolen’ from it by the balloon driver (vmmemctrl), at the same time
swapping was occurring and this could cause performance problems.
Cluster Memory
The next place to look at for memory issues is at the Cluster.
It is useful to look at:
–
Average memory usage of total memory available
–
Average amount of memory used by memory control
–
Average memory shared across the VM’s
–
Average swap space in use
In the graph below we can see that when the shared memory drops the
individual memory usage increases.
In addition to that swapping and memory control increased at the same
time.
On Friday join me as I discuss storage latency. In the meantime we've got some great white papers and webinars on VMware Capacity Management - join our Community and get free access to them http://www.metron-athene.com/_resources/index.html
Phil Bell
Consultant
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