Resource Pools: What is a few examples of when this could be used

Deathmage

Hey guys,

So I understand what a Resource Pool is but what is the benefits and/or the use of having a Resource Pool vs just having the VM's directly on the esxi host. What would be some examples of it's use?

Essendon

Uses:

- You have a number of customers on the same IaaS platform and you want to guarantee resources.
- Set of VMs that need guaranteed access to resources. Say you have a critical multi-tiered application, you may want to create a pool for the VMs
- Access control/delegation perhaps? Not a good use though.

Cant think of any others. Whatever you do, don't use them as folders and keep an eye on utilization within the pool.

dave330i

You can use it to collapse the number of clusters which increase the available compute resources by reducing the # of n+1 servers.

Deathmage

So in essence to make sure I understand it a fine example would be say a Exchange cluster that resides within a host that say has 20 others servers in a hoggpage of roles like DNS, FS, PS, DHCP, SQL, etc that has say just ballparking 2 xeon's at 2.87ghz so 16 logical cores and say 192 GB of RAM. So since is a large network I'll presume they have 450 users with inboxes, so 8 GB's per 250 mailboxes for lets say we give each server 32 GB's of RAM (16 GB's is needed plus a 16 GB buffer).....

so with the above said a Resource pool guarantee's that the Exchange Cluster of two servers inside of the pool always, always, always get the memory set for them. ... am I understanding this correctly?

Now what happens if the HA of the pool sucks up all the memory for the Exchange cluster and leaves none for the VM's aka servers outside of the pool?

Essendon

You are mostly correct. How resources work in a pool are like this - VM1 usually uses say 16GB RAM and if suddenly wants say 32GB, the pool hands it out. Then when VM1 doesn't need it any more the RAM flows back in to the pool for other members of the pool. It's best to set shares inside resource pools so in times of contention VMs with higher shares get more.

If there are say 10 Exchange servers that need serious grunt, it might be better to put them in a cluster of their own. Sure there's a slight increase in overhead but that way your dead certain no other VM will victimize your Exchange servers (at least compute-wise, you still gotta watch your storage and network).

I didnt quite get what you meant by the last sentence in your post. HA is for a cluster, not a pool. HA doesnt starve other objects of resources, it is a mechanism to get your VM's going on another host when a host fails. The resultant effect is that the number of VM's on each remaining host increases and each VM then gets less resources to play with. Make sense?

Deathmage

Essendon wrote: »

You are mostly correct. How resources work in a pool are like this - VM1 usually uses say 16GB RAM and if suddenly wants say 32GB, the pool hands it out. Then when VM1 doesn't need it any more the RAM flows back in to the pool for other members of the pool. It's best to set shares inside resource pools so in times of contention VMs with higher shares get more.

If there are say 10 Exchange servers that need serious grunt, it might be better to put them in a cluster of their own. Sure there's a slight increase in overhead but that way your dead certain no other VM will victimize your Exchange servers (at least compute-wise, you still gotta watch your storage and network).

I didnt quite get what you meant by the last sentence in your post. HA is for a cluster, not a pool. HA doesnt starve other objects of resources, it is a mechanism to get your VM's going on another host when a host fails. The resultant effect is that the number of VM's on each remaining host increases and each VM then gets less resources to play with. Make sense?

thanks for the explanation...

I meant in the last sentence like say the pool is set for 64 GB's (32 per server) but grows to say 40 on one server and then sucks the other 8 GB's for the 2nd server in the pool from the host, leaving say I dunno 16 GB's of ram left over for say 3 other VM's that each normally have 8 GB's would the other VM NOT in the pool and (just on the esxi) fault out or would the pool fault.
Like to me a pool has a higher priority of memory over VM's not in the pool in the host.

Essendon

These are good questions, I suggest you read the resource pool section in the Mastering vSphere book and lab it up as you go. Things will be far clearer if you saw them happening yourself.

Deathmage

Essendon wrote: »

These are good questions, I suggest you read the resource pool section in the Mastering vSphere book and lab it up as you go. Things will be far clearer if you saw them happening yourself.

Indeed, labbing slowly but surely through the bookie..