I'd like a clarification on CS planner algorythms

[akrasnov-drv]

Hi,
I have quite a weird problem.
I want each new VM to start on another host.
I tried using random planner, then switched to userdispersing, added the setting also to storage, everything to no avail.
VMs are created on the same host in blocks, e.g. 5 VMs on the same host in a raw, then another host, but keeping use just of this 2. And just after some time it continues to additional host.
I have no problem to start VM on particular host by specifying it in VM deployment. But if I allow CS to choose, it does the above.
If it changes anything, I have single cluster and single pod, and I use local storage for VMs.

Here are settings I tried:

• vm.allocation.algorithm (random, userdispersing)
• vm.deployment.planner (userdispersing)
• deployment.planners.exclude (removed some defalut values keeping just SkipHeuresticsPlanner)
• deployment.planners.order (moved UserDispersingPlanner to be the 1st)
• image.store.allocation.algorithm (random)

Please explain/advise.

[rajujith]

@akrasnov-drv vm.allocation.algorithm = userdispersing should work. No need to change the vm.deployment.planner. You also try anti-host affinity in affinity groups.

[akrasnov-drv]

Unfortunately I can't use anti-affinity groups as jCloud plugin does not support using that.

I already have vm.allocation.algorithm = userdispersing and just now got 9 of 10 new VMs on the same host (cluster had 5 hosts and just 1 VM running)

What other parameters influence on host choice?
Maybe there is a bug?

[rajujith]

All of the 9 instances belong to the same Account? This works per Account.

[akrasnov-drv]

yes, 1 have only admin account, 1 cluster, 1 pod, 5 hosts
just now I started 10 instances via jcloud plugin and all 10 started on the same host.
To make sure I'll try to run 10 from cli.

[akrasnov-drv]

The same via cli
9 of 10 from the same host (another one then in the previous test) and then 1 from a different host (the above 1) .
Each time I get 10 VMs from the same 2 hosts, other 3 are not used at all for the first 10 VMs.
Hosts configuration is different, so looks like planner uses host free resources / use history to decide where to place VMs.
Neither random nor userdispersing strategies change this.

[akrasnov-drv]

I proceeded with tests without removing running VMs
I executed 3 cycles each of 10 VMs with delay of 1 sec
First I've got 9 from one host, then 11 from another host, and finally 10 more on the 3rd host
each host was used continuously

[akrasnov-drv]

When planner chooses a host, what stats it uses? And how often the stats are updated?
Maybe for some set of data it uses exactly the same algorithm and chooses the same way the same host (till data is not refreshed)?