IBM z13s, Technical Manual

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Appendix F. KVM for IBM z Systems
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platform mobility easier. Its live relocation capabilities enable you to move virtual machines
and workloads without incurring downtime.
Table F-1 shows the features that are supported by KVM for IBM z Systems.
Table F-1 Supported features in KVM for IBM z Systems
F.2 IBM z Systems servers and KVM
The z Systems platform is highly virtualized, with the goal of maximizing the utilization of
compute and I/O (storage and network) resources, and simultaneously lowering the total
amount of resources needed for your workloads. For decades, virtualization has been
embedded in the z Systems architecture and built into the hardware and firmware.
Virtualization requires a hypervisor, which manages resources that are required for multiple
independent virtual machines. Hypervisors can be implemented in software or hardware, and
the z Systems platform has both. The hardware hypervisor is known as IBM Processor
Resource/Systems Manager (PR/SM). PR/SM is implemented in firmware as part of the base
system. It fully virtualizes the system resources, and does not require extra software to run.
KVM for IBM z is a software hypervisor that uses PR/SM functions to service its virtual
machines.
PR/SM allows the defining and managing of subsets of the z Systems resources in logical
partitions (LPARs). Each KVM for IBM z instance runs in a dedicated LPAR. The LPAR
definition includes a number of logical processing units (LPUs), memory, and I/O resources.
LPUs are defined and managed by PR/SM and are perceived by KVM for IBM z as real
CPUs. PR/SM is responsible for accepting requests for work on LPUs and dispatching that
Feature Benefits
KVM hypervisor
Supports running multiple disparate Linux virtual
machines on a single system
CPU sharing
Allows for the sharing of CPU resources by virtual
machines
I/O sharing
Enables the sharing of I/O resources among virtual
machines
Memory and CPU over-commitment
Supports the over-commitment of CPU, memory,
and swapping of inactive memory
Live virtual machine relocation Enables workload migration with minimal impact
Dynamic addition and deletion of virtual I/O
devices Reduces downtime to modify I/O device
configurations for virtual machines
Thin provisioned virtual machines Allows for copy-on-write virtual disks to save on
storage
Hypervisor performance management Supports policy based, goal-oriented management
and monitoring of virtual CPU resources
Installation and configuration tools Supplies tools to install and configure KVM for IBM
z Systems
Transactional execution exploitation Provides improved performance