Probably most people working in IBM z or Linux One environments already know the IBM z/VM Hypervisor.
z/VM born in the 2000 derived from the IBM experience in term of virtualization, typical of s390 architecture. The z/VM evolves during these 20 years and now it’s a very solid Hypervisor.
Unfortunally it run only on the IBM z Architecture, this from one side, permits to be very efficent and fast, but, on the other side, the diffusion and the knowledge of this hypervisor is very limited. The skills needed to operate on z/VM environment are very specific and have very few things in common from the operations of a typical distributed environment.
So if a company decide to use Linux on IBM z running z/VM needs to acquire resources with very specific knowledge on this hypervisor, and probably these type of resources are very expensive e very low integrated with other platforms knowledges.
Probably so far the IBM z/VM is the best hypervisor on z architecture, but in the last years an open source hypervisor is becoming more standard also in the IBM z environments, it’s the KVM hypervisor.
KVM (Kernel-based Virtual Machine) is an opensourec hypervisor, and it's part of linux itself, infact his modules are integrated in the Linux kernel natively.
One great thing of KVM is that it's distributed, without additional costs, as standard kernel module in the major Linux distributions (RedHat, Ubuntu, Suse), it’s cross architecture, so you can find the KVM also on x86, Power and Arm environments, so is not architecture specific and doesn’t need specific knowledge to operate. This is a very good news for the Companies wants to invest on Linux on Z environments, because don’t need to hire expensive resources to operate, but can also reuse the pre owned resources currently operate in x86 environments.
KVM is also used as “building block” of many hybrid cloud implementations, and represent the standard virtualization hypervisor used also in Openstack, Nutanix, Ovirt solutions.
The KVM on IBM z and Linux One is a very good choice to build a Linux environment on IBM z because it is very flexible, standard and very easy to operate, it shares a lot of code with the x86 variant, so it’s a market standard Hypervisor.
It permits many interesting features like VM snapshots, VM Cloning, VM live migration from two different hosts, supports live resize of CPU, Networking and storage devices in both KVM hosts and guest virtual servers and permit also nesteded virtualization (KVM on KVM).
KVM uses all the specific hardware feature of IBM z and Linux One architecture, such as CPACF crypto hardware facility and CryptoExpress cards on both Hosts and VM guests, supports Java pause-less Garbage Collection, can use FlashExpress as swap storage for KVM hosts, can use any kind of SAN (FICON and/or FC) and still use SAP processor to offload the I/O overhead from IFL CPs.
The KVM environment can be easily managed using the virsh commands from linux libvirt command shell and also using gui as Virt-Manager or Cockpit web interface virtual machine plugin.
So using KVM on z you have all the IBM z specific stuff of this architecture with the flexibility and the openness of most important opensource hypervisor.
This open source technology also helps people working on distributed environments to be interested also to IBM z environment because with KVM implementation now the z architecture is more open and standard, and more similar to the infrastructure they daily operate.
Most specific KVM for IBM z code is developed from a IBM Team in Germany, I had the opportunity to know some of them, and I’ve to say that they are incredible, very passionate and very focused on the project, aiming to large diffuse this hypervisor on this platform. So the KVM code is live and upgraded every day!
KVM open the Linux on Mainframe environment to the Hybrid Cloud, permits to IBM z to be a standard architecture on this cloud. Dramatically reduce the IBM z specific and expensive skills and permit to Linux environments to gain all benefits of this platforms, such as vertical scalability, resiliency, security and interoperability.
Redhat also investing on this hypervisor on z extendending (on last July) the support for unlimited KVM guests, High Availability, Insights and smart managment.
If you are interest on this technology there is a recent IBM Redbook explain all the possibilities of KVM on z.
http://www.redbooks.ibm.com/redbooks/pdfs/sg248463.pdf
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Diego D'Addeo - IBM z Champion 2020
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