How to change virtual machine limits in vCloud Director

By default, vCloud Director does not limit the size of memory, disks and number of vCPUs when creating a new virtual machine. This means the global configuration maximums for vSphere apply, which can be a problem for a service provider. Depending on the settings in the allocation model that a SP uses.

With vSphere 6.5 and 6.7 the configuration maximums for virtual machine sizing are as follows:

  • Memory: 6128 GB
  • vCPUs: 128
  • Disk size: 62 TB

(see https://configmax.vmware.com/guest)

And this is the point where trouble begins: If a customer can create virtual machines with 62 TB disks, it’s only a matter of time until the datastore is full and all other customers are affected.

So, if you want to limit these virtual machine configuration maximums in vCloud Director (above 8.10), you have 2 options:

  • First, you can set quotas in the allocation model settings for the whole Organization VDC.
  • Second, you can use cli commands to set a global limit for the maximum size of vCPU, memory and virtual disks.

But even if you can set quotas for the whole Organization VDC, it makes sense to limit the global configuration maximums in vCloud Director. Or who needs to roll out virtual machines with 62 TB disks or 6 TB of memory?

For changing the global configuration limits for vCPU, memory and disk size, you have to login to a vCloud Director cell via SSH first.

After login you can use the cell-management-tool  to adjust the config values:

$VCLOUD_HOME/bin/cell-management-tool manage-config -n vmlimits.disk.capacity.maxMb -v 2000000

This command sets the maximum virtual disk size to 2 TB (2.000.000 MB).

And the settings in this example

$VCLOUD_HOME/bin/cell-management-tool manage-config -n vmlimits.cpu.numcpus -v 32
$VCLOUD_HOME/bin/cell-management-tool manage-config -n vmlimits.memory.limit -v 131072

will limit maximum size of a VM to 32 vCPUs and 128 GB RAM.

VM with resources set above the limit will fail to be powered on with an error:

“The operation could not be performed, because there are no more {CPU|Memory|Disk} resources.”

 

Notes:

  • These commands need only be executed on one node and they take immediate effect. Nothing needs to be restarted.
  • These configuration changes only affect newly created virtual machines. Existing virtual machines are not affected.
  • The disk limitation do not apply to system administrators. The memory and vCPU limits do apply to system administrators.

 

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