Don't count out IBM virtualization on the Z platform
A mainframe can house hundreds of thousands of VMs and a wide range of workloads. Also, IBM Z provides virtualization management via Dynamic Partition Manager and Wave for z/VM.
Under the right circumstances, IBM virtualization on the Z platform could lead to more efficient workflows and streamlined operations, especially with some of the improvements in the z14 system.
IT teams that support server virtualization commonly rely on x86 computers or similar systems to deploy their virtualized workloads, but some teams might benefit from IBM's latest generation of mainframe computers: IBM Z. The Z platform provides extensive support for both hardware- and software-based virtualization, making it possible to deploy a wide range of workloads from a single environment.
With the Z platform, IBM virtualization is embedded directly into the mainframe architecture at the hardware, firmware and software layers. Integral to this technology are the hypervisors that provide the control code necessary to manage resources across multiple OS images. The images run independent of each other, controlling their own logical resources, which the system abstracts from the mainframe hardware.
The Z platform can support multiple hypervisors operating simultaneously, whether the same or different ones, providing a great deal of flexibility for implementing varied workloads and accommodating today's dynamic application environment.
Hardware-based virtualization
Underlying all virtualization on the Z platform is the PR/SM layer, a Type 1 hardware hypervisor that runs directly on the mainframe's bare metal.
Underlying all virtualization on the Z platform is the Processor Resource/Systems Manager (PR/SM) layer, a Type 1 hardware hypervisor that runs directly on the mainframe's bare metal. PR/SM is a virtualization technology that's encapsulated into the firmware to provide a secure abstraction layer for running multiple OSes on the same physical platform.
The PR/SM layer makes it possible to create logical partitions (LPARs) that administrators can configure with different OSes. IBM z14 supports up to 85 LPARs. Each LPAR runs its own OS and includes logical processor and memory resources, along with logical I/O devices for both networking and storage. Admins can define the amount of resources available to each LPAR and modify those amounts after they deploy the LPARs.
IBM virtualization offers multiple OSes that run on the Z platform, any of which admins can install in an LPAR, including the three basic Z OSes:
z/OS: Often viewed as the Z platform's default OS, z/OS provides a wide range of features for securely delivering mission-critical workloads. IBM designed the OS to ensure that applications and data remain available, while maximizing resource utilization.
z/VSE: The z/Virtual Storage Extended OS has its roots in the Disk Operating System. As such, it provides a smaller and less complex system than z/OS. The z/VSE OS is well-suited to batch and transaction processing operations that support routine production workloads running multiple jobs in parallel.
z/TPF: The z/Transaction Processing Facility OS targets high-volume, high-throughput transactional workloads, such as those generated by airline reservation systems or credit card processing centers.
In addition to the IBM OSes, admins can configure an LPAR with any one of the following Linux distributions: Red Hat Enterprise Linux for IBM System Z, SUSE Linux Enterprise Server for Z Systems and LinuxONE, and Ubuntu Server for IBM LinuxONE and IBM Z.
The Linux distributions are optimized to take advantage of the strengths and capabilities built into the Z platform, such as the pervasive encryption features. At the same time, the distributions make it possible to run the full range of Linux-based systems on a mainframe platform, providing IT with a robust environment for implementing Linux applications such as SAP, Oracle DB, Docker, Elasticsearch and Hyperledger Fabric.
The PR/SM layer makes it possible for IT to run any combination of the supported IBM and Linux OSes simultaneously. In addition, an LPAR can run a special type of IBM or Linux OS that serves as a software-based hypervisor, adding more flexibility to the Z platform's virtualization capabilities.
Software-based virtualization
Software-based hypervisors run in individual LPARs, just like the other OSes. IT can implement multiple instances of each hypervisor at the same time, along with LPARs running nonhypervisor OSes. Each hypervisor can support multiple VMs, also configured with different OSes. In this way, a single mainframe can support hundreds of thousands of VMs and a wide range of workloads, without being locked into any one OS ecosystem.
An LPAR can run one of two types of software-based hypervisors: IBM's z/VM or a KVM-enabled Linux distribution.
IBM's z/VM is a Type 2 hypervisor that can run multiple VMs, each configured with its own OS. The VMs can run any combination of the IBM and Linux OSes mentioned previously: z/OS, z/VSE and z/TPF, as well as the Red Hat, SUSE and Ubuntu distributions. The hypervisor provides high levels of resource sharing, I/O bandwidth, availability and data-in-memory capabilities.
KVM is also a Type 2 hypervisor that provides open source virtualization capabilities. Red Hat, SUSE and Ubuntu all offer Linux distributions that include a KVM module optimized for the Z platform. At one time, IBM virtualization included a version of KVM, but this was discontinued in early 2018.
The KVM hypervisor can benefit organizations already running workloads based on x86 KVM that want to transition to mainframe environments as easily as possible. The hypervisor supports most of the same features as z/VM and works much the same way as x86 KVM, so the transition should be relatively straightforward. However, organizations looking for deeper integration with the Z platform might instead opt for z/VM, which is designed specifically for the Z infrastructure.
Server virtualization on the Z platform
IBM virtualization is supported by several features on the Z platform. For example, the platform includes the Dynamic Partition Manager, a feature for simplifying virtualization management at the PR/SM layer. IBM also offers Wave for z/VM, another system for simplifying virtualization management, but this one is specific to the z/VM hypervisor.
A mainframe computer isn't for everyone. It's a big investment and requires IT professionals who know their way around the Z environment, making it much more suited to larger enterprises running critical workloads, especially those that rely heavily on server virtualization.
