Plain Virtualization

NUMA is always a very interesting topic when in design and operation in virtualization space.  We need to understand it so we can size a proper VM more effectively and efficiently for application to perform at its optimum. To understand what is NUMA and how it works, a very good article to read will be from here .  Mathias has explained this in a very simple terms with good pictures that I do not have to reinvent.  How I wish I have this article back then. Starting from ESX 3.5, NUMA was made aware to ESX servers.  Allowing for memory locality via a NUMA node concept.  This helps address memory locality performance. In vSphere 4.1, wide-VM was introduce this was due to VM been allocating more vCPUs than the physical cores per CPU (larger than a NUMA node).  Check out Frank's post . In vSphere 5.0, vNUMA was introduced to improve the performance of the CPU scheduling having VM to be exposed to the physical NUMA architecture.  Understanding ho...

While I was reading up the vSphere 5 Clustering Technical Deep Dive book by Duncan Epping and Frank Denneman, I came across this section which took me to awhile to understand the calculation for the math part. This section on memory share which has been changed in vSphere 5 which is also written in Frank Denneman, Mem.MinFreePct sliding scale function. The example is as below: Let’s use an example to explore the savings of the sliding scale technique. On a server configured with 96GB RAM, the MinFreePct threshold will be set at 1597.6MB, opposed to 5898.24MB if 6% was used for the complete range 96GB. Free memory state Threshold Range Result High 6% 0-4GB 245.96MB 4% 4-12GB 327.84MB 2% 12-28GB 696.32MB 1% Remaining memory 696.32MB Total High Threshold 1597.60MB I was trying to get the calculation for the Result column and thought to elaborate it on a clearer picture which a believe some are confused like myself. The first 0-4GB wi...

The new licensing scheme is used in vSphere 5. Unlike in vSphere 4, where vRAM is not taken into consideration rather the number of cores per socket. Let do a refresh. In vSphere 4, for Enterprise edition is entitled to 6 cores per physical processor per server. For Advanced/Enterprise Plus edition, is entitled to 12 cores per physical processor.  As for the RAM limitation will be 256GB memory per host except Enterprise Plus which is unlimited. An example would be follows: 1 server with 2 physical CPUs, each with 8 cores. This will require 2 x Enterprise Plus license. If you apply 2 x Enterprise instead of Enterprise Plus license, only 6 cores per CPU will be used and 2 cores per CPU left idle. Let's talk about vSphere 5 licensing. Before we begin, vSphere 5 have removed Advanced edition. A customers who is on Advanced Edition on vSphere 4 will be upgrade to vSphere 5 Enterprise. vRAM entitlement is based on an edition per physical CPU (no more limitation of number...