Vertical scaling support matrix (by type of pattern and platform)

Vertical scaling is the process of dynamically increasing or decreasing the processor, RAM, or disk of a virtual machine. Cloud Pak System supports dynamically increasing processor and RAM on virtual machines.

You can manually increase the disk size for a virtual machine in the console. This section describes vertical scaling support by type of pattern (virtual application or virtual system) and platform.

The following table describes vertical scaling support for virtual application patterns and virtual system patterns.

Table 1. Virtual application patterns and virtual system patterns - vertical scaling support
Platform Hot-add CPU Hot-remove CPU Hot-add memory Hot-remove memory Add or remove storage
Linux Supported Not supported Supported Not supported Not supported with auto scaling; however, you can add a disk in the console for each virtual machine
Windows system Supported Not supported Supported Not supported Not supported with auto scaling; however, you can add a disk in the console for each virtual machine

The following table describes vertical scaling support for classic virtual system patterns.

Table 2. Classic virtual system patterns- vertical scaling support
Platform Hot-add CPU Hot-remove CPU Hot-add memory Hot-remove memory Add or remove storage
Linux Supported Not supported Supported Not supported Not supported with auto scaling; however, you can add a disk in the console for each virtual machine
Windows system Supported Not supported Supported Not supported Not supported with auto scaling; however, you can add a disk in the console for each virtual machine

Limitations

  • Increasing allocated CPU or memory resources might require restarting the middleware or virtual machine. When using Cloud Pak System, certain limitations exist when scaling the allocated memory or number of CPUs of a deployed virtual machine that is powered on. You might see the error CWZIP1987E in log files.
    Because of these limitations, you might need to take additional steps when any of the following situations apply:
    • The allocated memory is less than or equal to 3 GB and you want to increase it to a value greater than 3 GB
    • You want to increase the allocated memory to more than 16 times the memory allocation when the virtual machine was last started
    • The current CPU allocation is one virtual CPU and you want to add more virtual CPUs
    • You want to increase the CPU allocation to a value greater than eight virtual CPUs
    Perform the following steps to modify the allocated virtual CPUs or memory size of the virtual machine:
    1. Stop the virtual machine instance.
    2. Resize the allocated memory or number of virtual CPUs.
    3. Restart the virtual machine instance.
  • The actual usable memory available to virtual machines is less than the total available memory shown on the compute nodes in the console because the hypervisor requires some amount of memory on each compute node. An additional amount of memory is also needed by the hypervisor for each running virtual machine. Finally, setting the Reserve resources for availability field on the cloud group to Yes enables the Cloud Pak System placement engine to reserve sufficient memory and CPU resources in the cloud group. Then, should a compute node fail or require a maintenance upgrade, each running virtual machine can migrate to other compute nodes in the cloud group.

    These factors limit the amount of memory for allocation that can be used by a virtual machine for vertical scaling.