Prerequisites for the VM Migration

A VM Migration requires the Server Units involved to fulfill some prerequisites. All hard- and software prerequisites are checked by Customer Service and, if necessary, corrected during installation of the SU cluster.

You will find information on hard- and software dependencies in the release notice for VM2000. There, you can also find further information on prerequisites and recommendations for VM Migration.

For a successful VM Migration, the following prerequisites have to be fulfilled in the current operation.

General prerequisite

Source and target SU are in an activated SU cluster.

Prerequisites for SU /390

• The main memory size of the VM2000 hypervisor is large enough on both the source and target SU, see HYPERVISOR-SIZE parameter in the section "Setting the VM2000 parameters in the parameter service".

  If the hypervisor size is insufficient, the VM Migration and, potentially, other hypervisor activities cannot be executed.

• The main memory size of the monitor VM is at least 512 Mbytes on both the source and target SU, see section "Configuration via the VM2000 configuration file (SU /390)". If the monitor system is working productively, the main memory size must be appropriately higher.

• The monitor system on both source and target SU has a suitable CPU capacity (multiprocessor VM, sufficient CPU quota, unrestricted CPU utilization).

  Insufficient main memory size or CPU capacity on the monitor VM prevent the VM Migration from being executed or from being executed efficiently.

• Source and target SU should have comparable I/O configurations. It is best to use an identical, if necessary “over configured”, IOCF, meaning a shared hardware generation for the I/O configurations of both Server Units, which may include connections for BS2000 devices that are not (yet) physically present on one of the SUs. The device configuration must at least be suitable for those devices that are to be allocated to a VM to be migrated.

VM2000 assumes that these prerequisites are met. They are not checked in the /CHECK-VM-MIGRATION and /MIGRATE-VM commands. These only check if the SU cluster is currently active and whether the I/O configurations of the devices allocated to the VM to be migrated are suitable.

Prerequisites for the source SU

• The monitor VM cannot be migrated.

• No other VM Migrations from this source SU and no VM2000 shutdown are currently being executed.

• Additional prerequisite if the VM to be migrated is in DOWN state:

  • The guest system was not terminated abnormally (SETS).

• Additional prerequisites if the VM to be migrated is in RUNNING state:

  • The guest system is ready to operate (“system ready”).

  • The VM has not been stopped with /HOLD-VM (SU /390).

  • The main memory of the VM is not currently being reconfigured.

  • There is currently no dynamic I/O configuration modification going on (SU /390).

  • The guest system supports the “Live Migration”.

VM2000 checks these prerequisites in the /CHECK-VM-MIGRATION and /MIGRATE-VM commands.

Prerequisites for the target SU

If the prerequisites for the source SU are met, VM2000 checks the following prerequisites for the target SU in the /CHECK-VM-MIGRATION and /MIGRATE-VM commands.

• There are currently no VM2000 shutdown and no VM Migration to this target SU being executed.

• The VM index (if explicitly stated while the VM was being created) and VM name are available, e.g. they have not been assigned to a different VM.

• The maximum number of VMs and VM definitions (SU x86) has not been reached.

• There is enough main memory for the VM to be migrated.

• If the VM to be migrated is assigned to a VM group (SU /390): the VM group exists.

• The CPU pool of the VM to be migrated or of the respective VM group (SU /390) exists and has at least one attached CPU.

• The assignment sets assigned to the VM to be migrated exist.

• The devices assigned to the VM to be migrated have the same device type on both SUs and can be assigned in the same usage mode (EXCLUSIVE/SHARED).

• Additional prerequisites if the VM to be migrated is in RUNNING state:

  • There is currently no dynamic I/O configuration modification going on (SU /390).

  • The devices of the VM to be migrated have a compatible path configuration (SU /390).

  • The attached disks of the VM to be migrated are ready to operate.

  • The disk devices of the VM to be migrated should have been generated in the same disk storage system, using the same device number (LUN). Otherwise, the warning VMS2472 is issued.