Basic Questions, Resource Pools & NIOC, easy points

[JPM300]

Hey all,

Just need some clarification on two things.

1.)  Child Resource Pools.  I know if you have the Expandable Reservation setting set to the Child resource pool it can use resources from a parent so say you had the following setup:

Parent RP - 12GB Memory reservation

VM1 - 2GB mem

VM2 - 2GB mem

VM3 - 2GB mem

     - Child RP - 6GB Memory reservation (Expandable Reservation) 

          VM4 - 6GB Memory

          VM5 - 2GB Memory

Lets say we have this setup.  Even with Expandable Reservation on, it wouldn't be able to start VM5 unless Vm3 was turned off correct? As if VM3 was off, there would be enough resources left in the Parent RP to supply the VM?

Also how far does the Expandable Reservation run.  For instance say I left the Parent RP set to an Expandable Reservation and the host had another 24GB of memory left that isn't being used.  If the Child RP takes resources from the Parent RP to the point where it can't supply its reservation will the Parent RP take from the hidden root resource pool on the host/cluster as it has the expandable option turned on?

However if Expandable Reservation is off, then the Child RP just has 6GB of memory reserved for it and whatever can run in there will have to run in.

2.)  NIOC with VDS

If you have a host with say 1 10GB nic.  This would never be the case due to single points of failure, but just for example sake lets just assume.  So 1 10GB Nic and you want to chop up the traffic with NIOC.  Lets say we chop up the traffic like such:

vMotion - 2GB

Backup - 2GB

iSCSI - 2GB

Backup - 1GB

VM Network - 3GB

Now if you add shares onto the NIOC they work in conjunction with the NIOC limits correct?  So lets say we want VM Network to have higher priority so we set the share value to High and leave everyone else at normal.  If network contention happens and the VM network is having problems supplying the 3GB of network throughput, it will win due to the share settings correct?

Just wanted some clarification on how NIOC plays with Shares as I've always done one or the other.

[JPM300 · Accepted solution]

So after looking into these items I have found the following information through colleges, testing, and some documentation.

1.)  Child resources pools can use resources from the Parent if the Expandable Reservation is set.  It can even pull resources from mulitple parents if it is a child from a few tiers down.  Or a better way of putting this is in the previous exam I posted VM4, and VM5 could pull resources from Parent RP assuming the Expandable option is set.  Vm4 and VM5 could even pull additional resources from the root hidden resource pool at the cluster level assuming there was free resources.   So its important to keep this setting in mind if you want to keep a solid number of resources set to a child resource poll.

2.)  With NIOC you can use both limits and shares in conjunction with each other, but there is a catch.  If you only use shares to control the bandwidth of each traffic type IE(vmotion, vmnetwork, backup, iSCSI, vmotion, ect)  If one of the traffic types is not using much or any traffic the other can borrow that traffic.  For instance say VM Network was getting hit with heavy network traffic and the rest of the traffic types where not using their bandwidth allocation of the share% then VM Network could use more, so VM Network could spike up to 8GB if something was pushing it that way.  However if another traffic type with a higher share needed that traffic again VM Network would have a lower priority and loose some of its traffic speed.

Now when it comes to limits, limits override the shares in the sense that if you set VM Network a 2GB limit, even if the other traffic types are not being used VM Network will still never be able to use more then 2GB.  However if you where to set VM Network with a limit of 2GB and a high share value while the other traffic types had normal or low traffic shares set, VM Network would get priority in the time of contention.  The problem with this is if EVERY traffic type has a limit set there will never be a time when contention happens, there for the shares kind of become moot.  The exception to this is if you where using a mix of the options.  So some limits set, with other traffic types set to share %.  Then the two options will play together nicely.  The only other scenario I can think of that would be able to leverage limits and shares would be if you set multiple traffic types to higher limits for example:

VM Network - 4GB limit

vMotion - 4GB Limit

iSCSI - 4 GB Limit

Backup - 2GB limit

In this case you could use shares to still set a preference to who should get priority over the traffic.

With that said unless someone else can correct me if hard limits are set for all traffic types I can't see the need to set shares?

A very good write up on how NIOC breaks down and works can be found here:

vSphere 5.1 – Network I/O Control (NIOC) Architecture - Old and New | VMware vSphere Blog - VMware B...