Nutanix

How To – AHV Acropolis Dynamic Scheduling

With introduction to AOS 5.0 Nutanix had release one of the most competing feature as ADS which makes AHV fully enterprise ready and more competing.

Acropolis Dynamic Scheduling or ADS will proactively monitors AHV cluster for compute and storage I/O and migrate VMs to avoid any hotspots similar to VMware DRS or Hyper-V SC PRO, but as built-in intelligence u don’t have much to worry about configuring it properly.

ADS will be enabled default and to verify run

acli ads.get

ads-get

can be disabled from acli using

acli ads.update enable=false

and can be re-enabled using

acli ads.update enable=true

so now ADS is enable whats next, set rules configure affinity rules.

Currently AHV supports VM-Host and VM-VM anti-affinity policy only.

VM-Host Affinity

Using VM-Host affinity you can make sure that VM will only be able to run on selected hosts only.

VM-Host affinity cannot be configured if you have HA set for reserved host.

To verify run acli ha.get

acli ha.get
..
 reservation_type: "kAcropolisHAReserveSegments"
..

verify reservation_type is not set as kAcropolisHAReserveHosts.

To set reservation_type as Reserve Segments run

 acli ha.update reservation_type=kAcropolisHAReserveSegments

To set VM-Host affinity you can select host list while creating VM or update VM later.

vm-host-affinity

and selecting hosts you want to set affinity to.

vm-hostlist-affinity

so now you have list of host that VM is allowed to run on.

vm-hostlist1-affinity

Now if you try to migrate that VM you will be allowed selected hosts only.

vm-hostlist-affinity-migrate

ADS will not allow to unset VM-Host affinity while VM is ON but you can do using acli

acli vm.affinity_unset vmname

VM-VM Anti-Affinity

VM-VM anti-affinity allows to make sure VMs will always run on different hosts. Currently it can be set using acli.

In order to define anti-affinity policy you have to create a VM Group and set anti-affinity on that group, so when the VMs are turned ON they are prefered to be on different host, but this policy does not limit ADS from taking action in resource constraints.

Create VM Groups

acli vm_group.create <vm_group_name>

vm_group-create

List VM Groups

acli vm_group.list

vm_group-list

Add VMs in VM Group

acli vm_group.add_vms webservers vm_list=<vm1_name>,<vm2_name>

vm_group-add_vms

List VMs in VM Group

acli vm_group.list_vms <vm_group_name>

vm_group-list_vms

Get VM Group Information to see Anti-Affinity Policy

acli vm_group.get webservers

vm_group-get_1

*Noticed no anti-affiity policy defined

Set Anti-Affinity Policy to VM Group

acli vm_group.antiaffinity_set <vm_group_name>

vm_group-set_affinity

Get VM Group Information to verify Anti-Affinity Policy

acli vm_group.get <vm_group_name>

vm_group-get_2

Now when the VMs will be turned they will be placed on different host.

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