Configure ESXi

NTP Configuration on ESXi Host


vSphere Client :

Web client

DNS and Routing Config


Using ESXi DCUI console :

 VC client

Hyper Threading 

Hyper threading is the advanced CPU feature available on Intel NEHALEAM  CPU series , which allows cpu to run two threads simultaneously.Its helps to improve the CPU performance by 0 - 40 % on supported systems.

Os can recognize  whether physical cores or Hyperthreded cores but application will not be able to distinguish .

ESX  Behavior:

Esxi scheduler can distinguish between the Physical cores and the hyperthreded cores. scheduler will allocate the physical cores untill physical cores are loaded .If there are additional vCPUs requesting CPU resources they will then be assigned to the additional logical cores. By this method HT has no impact on performance until more vCPUs are concurrently executing than there exist physical cores.



To enable Hyper-threading , this need to be first enabled in the BIOS of the host . 

Configuration using vSphere client:

Hyperthreading - web client

Hyperthread config for VM 

VM level sharing  :

1. Any - Default - allows VMs to share virtual core from other VMs as well. This is set by default.
2. None -Virtual Machine get exclusive access to the core the other thread who wants to access the core has to wait.
3. Internal  -VMs are allowed to share cores from the same physical cores

Memory compression cache
 ESX Uses Memory compression techniques i.e GZIP to extend the use of RAM which will reduce the swapping of memory pages . Memory compression is enabled by default and improves the performance when over-committing the memory by limiting the swap to disk .This technique divide VM swapping memory to 4KB and tried to compress them to 2KB. If compress success, then, you can save 50% space, if it fails, VM still swap the original 4KB to physical disk.

Enabling/Disabling Memory Compression

Open the Virtual Center and select Hosts and Clusters

Select a host and click the Configuration tab

Select Software | Advanced Settings

Select Mem.MemZipEnable, 1 for on, 0 for off

Configuring Memory Compression

Open the Virtual Center and select Hosts and Clusters

Select a host and click the Configuration tab

Select Software | Advanced Settings

Select Mem.MemZipMaxPct. 

This defaults at 10% of the RAM for caching and can be altered from 5% to 100%

Note : Compression process uses 2 - 3 % of Host CPU and time of compression is 20 ms. Compressed Memory is placed in the VM Memory not the Host Memory .



ESXi Licensing

You can add any number of licenses to  vSphere environment using the vsphere license key. Esxi license is socket based . There is not more restriction on the Memory ( vRAM entitlement )

Home => Administration => Licensing => Manage Vsphere License => Add license key