DRS vs Resource pool

[alankoh]

Hi all

Can't wrap my head fully around resource pool vs DRS

Assuming i am using resource pool to allocate shares to make sure that certain pool get sufficient CPU resources during contention - how does DRS come into play in such scenario ?  will it suggest to migrate vm in another pool with lower shares to be migrated to another host ?

If DRS is already making sure that all the VMs are migrated to hosts with sufficient resources - how does resource pool come into play ?

q1) Can i say that the sequence of control to be

1) DRS - to make sure all VMs get their required resources

2) Resource pool - If VMs cant get their required resources even after DRS then at least use pool to make sure certain VMs get better preference ?

q2) in a ESXI cluster, since a VM is only able to get compute resource on the host it is running on - how does a resource pool actually calculate the and share the cluster resource as a whole ?

e.g. 2 hosts in a cluster with total 8 cpu resource a cluster / 4 cpu per host

how can i create 2 pools in the cluster to make sure that the cpu allocation are in 5:3 ratio, since in 1 host can only have a max of 4 actually running cpu ?

Thank you

[scott28tt]

@alankoh 

Moderator: Moved to vMotion & Resource Management Discussions, matter not specific to ESXi.

[sjesse]

Resource pools require DRS so its not one vs the others, but resource pools are more for when your run out of resources on a specific host and drs is about placement of vms in the cluster,

[alankoh]

Hi sjesse

Thanks for the reply

Just to side-track - do you have any idea of the use case in using an esxi cluster without turning on HA and DRS ?

[sjesse]

Each has it use, HA I leave off on VDI clusters, you don't really need it. DRS you don't really need to leave off in most cases but there are cases where you leave it at a very low level where it basically off unless you but a host in maintenance mode. The most likely cause is when you would leave DRS is if you had had a cluster where you would want all the vms tied to a specific host.   It all really depends on what you need, they aren't required unless you need them.                                                                                                               

[alankoh]

Hi sjesse

Thanks for your reply

What I meant is - if a esxi cluster is of any use if it does not have HA and DRS turn on ?

[depping]

No, then there's no real value in creating a cluster, you may as well have the hosts in vcenter without the cluster object. some people just then like to use the cluster object as a grouping mechanism.