Cluster Resource allocations

Posted on 2014-02-21
Last Modified: 2014-04-13
Anyone to explain the meaning of those columns in Resource Allocations? some of them are clear , but some not , especially ones that are related to the shares.

I also want to know if I reserve X MBytes memory for a VM, how would I know if I am violating the HA policy….I mean there would be not enough resources for HA failover to occur ?

Question by:jskfan
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LVL 121

Assisted Solution

by:Andrew Hancock (VMware vExpert / EE MVE^2)
Andrew Hancock (VMware vExpert / EE MVE^2) earned 500 total points
ID: 39877689
You would violate a HA Policy, if the remaining hosts in the Cluster, did not have enough RAM (Memory) available to satisft all your Reservations.

A Memory Reservation is a GUARANTEED RING FENCE resource for that VM.

So if you gave it a reservation of 64GB, and your hosts had a total memory of 64GB per Host, this would violate the HA Policy.

Do you need to use Memory Reservations?

Author Comment

ID: 39877734
Sometimes Resource Allocation is already setup by previous Admins,
I want to know the meaning of those columns, and where to check to make sure that HA failover is not violated…..
LVL 121
ID: 39877871
Can you upload a screenshot, and put question marks, around the columns, you need explaining?
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Author Comment

ID: 39878644
I believe VMHA has admission control that detects if resource reservation are respected

LVL 121
ID: 39879026
So you would like to know, what all these columns mean?

This is a large topic area, and rather than me cut and paste, the information you require can be found in this document

from Page 13, Chapter 2 - Configuring Resource Allocation

vSphere Resource Management

Author Comment

ID: 39879294
Columns related to Share /Shares, what do they represent ?
and worst case allocation column
LVL 121
ID: 39879307
Shares relate to "pieces" of a cake, the more cake/shares you get the higher priorty the VM get resources, when competing for resources. (e.g. when many VMs are competing for resources)

Worst Case, is what is predicted to be the resources your VM will get, based on all the other VMs, allocations.

VMware defines it as:-

Worst Case Allocation
The amount of memory resources allocated to the virtual machine based on user-configured resource allocation policies (for example, reservation, shares and limit), and with the assumption that all virtual machines in the cluster consume their full amount of allocated resources.


Author Comment

ID: 39880861
The columns Reservation and Shares(High,Normal,low,etc..) can be determined, but the Shares value, percent share , I am not sure how you can determine the values, in other words based on what factors , you set up share value to 5000 or to 80%

Author Comment

ID: 39881628
I also want to understand, if the provisioned Memory size for a VM is 4GB ,but under Reservation MB , at the ESX host level(Resource Allocation), you give the same VM 1GB…
Would the actual size of the VM be 5GB RAM  or 4-1=3 GB of RAM?
LVL 121
ID: 39982355
If you give a memory reservation of 1GB, this memory is guaranteed! The VM will always get 1GB allocated.

The Total Size will always be 4GB, but with 1GB reserved.

Author Comment

ID: 39983209
And you cannot reserve more than what has been assigned(4gb)?
LVL 121

Accepted Solution

Andrew Hancock (VMware vExpert / EE MVE^2) earned 500 total points
ID: 39983212
No, you would need to increase the memory of the VM, and then create a reservation.

You cannot reserve more than what has been set for the current RAM requirements.

Author Closing Comment

ID: 39997496
Thank you

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