Monday, May 9, 2016

Top vBlog 2016

vSphere-Land is running the Top vBlog 2016. This is to recognize and rank contributions in virtualization blogging. The Top vBlog voting contest helps rank the most popular blogs based on your votes and the outcome determines the ranking that is published on the vLaunchpad website.

The people who contribute content to the vibrant virtualization community share their experience, knowledge, and passion to help each other out. If you find our contributions valuable, please take the time to vote for your favorite blogs this year.


DRS Advanced Settings

Recently, I performed a study on DRS, which focused on workload placement of virtual machines to load balance a cluster.

It demonstrated that by using DRS advanced options, we are able to balance memory usage across a cluster. In my next blog post, I examine memory consumption (usage) vs active memory (demand); and discuss the importance of understanding the difference and the impact on workload placement.

Key Terms

Active (Demand) - Amount of memory that is actively used, as estimated by the VMkernel based on recently touched memory pages.
  • Virtual machine:   Amount of guest “physical” memory actively used.
  • Host:  Sum of all active metrics for all powered-on virtual machines plus vSphere services (such as COS, vpxa) on the host.
Granted - The amount of machine memory or “physical” memory that is mapped for a virtual machine or a host.
  • Virtual machine:   Guest “physical” memory that is mapped to machine memory. Includes shared memory amount. Does not include overhead.
  • Host:   Sum of all granted metrics for all powered-on virtual machines, plus machine memory for vSphere services on the host.
Consumed - Amount of memory consumed by a virtual machine, host, or cluster.
  • Virtual machine:   Amount of guest physical memory consumed by the virtual machine for guest memory. Consumed memory does not include overhead memory. It includes shared memory and memory that might be reserved, but not actually used. Use this metric for charge-back purposes.
    vm consumed memory = memory granted - memory saved due to memory sharing
  • Host:   Amount of machine memory used on the host. Consumed memory includes Includes memory used by the Service Console, the VMkernel, vSphere services, plus the total consumed metrics for all running virtual machines.
    host consumed memory = total host memory - free host memory 
Usage - Memory usage as percentage of total configured or available memory.
  • Virtual machine:   Percentage of configured virtual machine “physical” memory.
    active ÷ virtual machine configured size
  • Host:   Percentage of available machine memory.
    consumed ÷ machine-memory-size
Idle – Consumed memory that is not actively used.

DRS Migration Thresholds – The threshold set to automatically migrate virtual machines from one host to another to optimize resource usage.
  • Level 1 – Apply only priority 1 migrations, vCenter will only apply recommendations that must be taken to satisfy cluster constraints like affinity rules and host maintenance.
  • Level 2 – Apply priority 1 and 2 migrations, vCenter will apply recommendations that promise a significant improvement to the cluster’s load balance.
  • Level 3 (default) – Apply priority 1, 2, and 3 migrations, vCenter will apply recommendations that promise at least good improvement to the cluster’s load balance.
  • Level 4 - Apply priority 1, 2, 3, and 4 migrations, vCenter will apply recommendations that promise even a moderate improvement to the cluster’s load balance.
  • Level 5 - vCenter will apply recommendations that promise even a slight improvement to the cluster’s load balance.

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