Hypervisor

Key Characteristics

• • Hardware Abstraction: A hypervisor abstracts the physical hardware resources (CPUs, memory, I/O devices) from the guest operating systems, presenting them with a virtualized view.
  • Resource Management: It allocates and manages the physical resources among multiple virtual machines or LPARs, ensuring fair sharing and preventing resource contention.
  • Isolation and Security: Each LPAR or VM operates in its own isolated environment, preventing interference between workloads and enhancing security.
  • PR/SM (Firmware Hypervisor): Integrated into the IBM Z hardware, PR/SM is a Type-1 (bare-metal) hypervisor that directly manages hardware resources and creates LPARs.
  • z/VM (Software Hypervisor): A Type-2 hypervisor (though often considered Type-1 in practice due to its direct hardware access and control capabilities when running as the primary OS on a machine), z/VM runs within an LPAR and can host hundreds or thousands of guest operating systems, including z/OS, Linux on Z, and even other z/VM instances.
  • Dynamic Resource Allocation: Allows for the dynamic adjustment of CPU, memory, and I/O resources to LPARs or VMs without requiring a system reboot, often referred to as Dynamic LPAR (DLPAR) for PR/SM.

Use Cases

• • Workload Consolidation: Running multiple z/OS images, Linux on Z instances, or other operating systems on a single physical mainframe to maximize hardware utilization and reduce operational costs.
  • Development and Test Environments: Providing isolated virtual machines for developers and testers, allowing them to work on different projects or versions of software without impacting production systems.
  • Disaster Recovery (DR): Facilitating rapid recovery by allowing entire LPARs or VMs to be moved or restarted on a backup system in the event of a primary system failure.
  • Running Diverse Workloads: Hosting a mix of traditional z/OS applications, modern Linux on Z containers, and z/VM itself for specialized services on the same mainframe.
  • System Upgrades and Maintenance: Performing rolling upgrades or maintenance on one LPAR/VM while others remain operational, minimizing downtime for critical applications.

Related Concepts