Category: CPU

Contention on lightly utilized hosts

Often I receive the question why a virtual machine is not receiving resources while the ESXi host is lightly utilized and is accumulating idle time. This behavior is observed while reviewing the DRS distribution chart or the Host summary tab in the vSphere Client. A common misconception is that low...

cpu-affinity-HT

Beating a dead horse - using CPU affinity

Lately the question about setting CPU affinity is rearing its ugly head again. Will it offer performance advantages for the virtual machine? Yes it can, but only in very specific cases. Additional settings and changes to the virtual infrastructure are required to obtain a performance increase over the default scheduling...

AMD Magny-Cours and ESX

AMD’s current flagship model is the 12-core 6100 Opteron code name Magny-Cours. Its architecture is quite interesting to say at least. Instead of developing one CPU with 12 cores, the Magny Cours is actually two 6 core “Bulldozer” CPUs combined in to one package. This means that an AMD 6100...

Impact of oversized virtual machines part 3

In part 1 of the series of post on the impact of oversized virtual machines NUMA architecture, memory overhead reservation and share levels are reviewed, part 2 zooms in on the impact of memory overhead reservation and share levels on HA and DRS. This part looks at CPU scheduling, memory...