Calculate and Create a custom slot size configuration

Slot size is comprised of two components, CPU and memory.

· vSphere HA calculates the CPU component by obtaining the CPU reservation of each powered-on virtual machine and selecting the largest value. If you have not specified a CPU reservation for a virtual machine, it is assigned a default value of 32MHz. You can change this value by using the das.vmcpuminmhz advanced attribute. )

 

https://pubs.vmware.com/vsphere-50/index.jsp#com.vmware.vsphere.avail.doc_50/GUID-E0161CB5-BD3F-425F-A7E0-BF83B005FECA.html

· vSphere HA calculates the memory component by obtaining the memory reservation, plus memory overhead, of each powered-on virtual machine and selecting the largest value. There is no default value for the memory reservation.

· Using webclient:

·

· Calculate failover capacity with the following formula:

·

· Ref#The-Unofficial-Official-VCAP5-DCA-Study-Guide.pdf

·

Slot Size Calculation

Calculate Number of Slots in my cluster :

 

Host 1:

 

Host 2:

 

Host 3:

 

To get the slot I need to know
Largest VM CPU & Memory :

 

Note I have to exclude memory overhead 85 MB

CPU Default slot size 111 Mhz

Number of CPU Slots = Total available CPU resource of ESX or cluster / CPU Slot Size

8 X2.792 = 22.336 X 3hosts = 67
GHz = 67000 MHz

76000 / 111 =
600 approx. which match with below information

 

Number of memory slots = Total available memory resource of ESX or cluster
minus memory used for service console & ESX system / Memory Slot size

182670 – (85″overhead”+9774″reserved capacity”) =172811 / 8192 “largest VM memory size” = 21.0950927734375

The most
restrictive number among CPU and Memory slots determines the amount of slots for this cluster. We have 600 slots available for CPU and 21 Slots available for Memory. So the
most restrictive number is 21

 

Notes From <http://www.vmwarearena.com/2012/07/ha-slots-calculation.html>

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About Ahmad Sabry ElGendi

https://www.linkedin.com/pub/ahmad-elgendi/94/223/559
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