Skip to content

Kubernetes on Z with PowerMax: Modern Software Running on Mainframe

Co-authored with Justin Bastin.

With the 2023 addition of Kubernetes on LinuxOne, you can scale, reduce TCO, and build the hybrid cloud your IT management requires. Combined with Dell PowerMax storage and its CSI driver, you get container orchestration with enterprise storage on mainframe hardware.

Benefits of Kubernetes on System Z and LinuxOne

When I was a customer, I consistently evaluated how to grow the technical influence of the mainframe platform. If discussing financials, I would evaluate the total cost of ownership (TCO) alongside various IT solutions. If discussing technical pain points, I would evaluate solutions that may alleviate the issue.

For example, when challenged with finding a solution for a client organization aiming to refresh various x86 servers, I searched online presentations, YouTube videos, and technical websites for a spark. The client organization had already identified the pain point. The hard part was how.

Over time, I found the ability to run Linux on a mainframe (called Linux on Z), using an Integrated Facility for Linux (IFL) engine. Once the idea was formed, I started baking the cake. I created a proof-of-concept environment, installed Linux and a couple of applications, and began testing.

The light-bulb moment came not in resolving the original pain point, but in discovering new opportunities :

  • Physical server consolidation : create a plethora of virtual servers when needed
  • License consolidation : certain x86 applications were licensed per engine. A quad-core x86 server may need four application licenses. I needed one license for my Linux on Z environment
  • Scalability : scale horizontally by adding more VMs and vertically by increasing network ports, memory, and storage
  • Reliability : mainframe technology has been known to be reliable, utilizing fault-tolerant mechanisms within the software and hardware to continue business operations

With Kubernetes providing container orchestration irrelevant of the underlying hardware and architecture, you can leverage LinuxOne benefits to deploy applications in a structured fashion :

  • Enablement of DevOps processes
  • Container scalability : one LinuxOne box with hundreds (if not thousands) of containers
  • Hybrid cloud strategy : LinuxOne servicing various internal business organizations with compute and storage needs

With Dell providing storage to mainframe environments with PowerMax 8500/2500, a Container Storage Interface (CSI) was created to simplify allocating storage to Kubernetes environments on Linux on Z.

Deploy Kubernetes

Linux on IBM Z runs on the s390x architecture. All software needs to be compiled for that architecture.

Luckily, Kubernetes, CSI sidecars, and Dell CSI drivers are built in Go. Since the early days of Go , portability and support of different OS and architectures has been a core goal. You can list compatible OS and architectures with :

go tool dist list

The easiest way to try Kubernetes on LinuxOne is k3s . It installs with a one-liner :

curl -sfL https://get.k3s.io | sh -

Build Dell CSI Driver

The Dell CSI Driver for PowerMax is composed of a container for all actions against Unisphere and mounting LUNs to pods, with a set of official CSI sidecars to interact with Kubernetes.

The official sidecars are published for multiple architectures including s390x. Dell publishes images for x86_64 only.

To build the driver, we first build the binary, then the container image.

Binary

Clone the driver from csi-powermax into your GOPATH. Build with :

CGO_ENABLED=0 GOOS=linux GOARCH=s390x GO111MODULE=on go build

Verify the output :

file csi-powermax
csi-powermax: ELF 64-bit MSB executable, IBM S/390, version 1 (SYSV), statically linked, Go BuildID=…, with debug_info, not stripped

Container

The distributed driver uses a minimal Red Hat Universal Base Image . There is no s390x-compatible UBI image, so we rebuild from a Fedora base :

# Dockerfile to build PowerMax CSI Driver
FROM docker.io/fedora:37

# Dependencies, followed by cleaning the cache
RUN yum install -y \
    util-linux \
    e2fsprogs \
    which \
    xfsprogs \
    device-mapper-multipath \
    && \
    yum clean all \
    && \
    rm -rf /var/cache/run

# Validate some CLI utilities are found
RUN which mkfs.ext4
RUN which mkfs.xfs

COPY "csi-powermax" .
COPY "csi-powermax.sh" .
ENTRYPOINT ["/csi-powermax.sh"]

Build the container image with docker buildx for cross-architecture support :

docker buildx build -o type=registry -t coulof/csi-powermax:v2.8.0 --platform=linux/s390x -f Dockerfile.s390x .

The last step is to update the image in the Helm chart values to point to the new image.

Et voila ! Everything else is the same as with a regular CSI driver.

Wrap-up, Limitations, and Disclaimer

Thanks to the open-source model of Kubernetes and Dell CSM, it is easy to build and utilize them for many different architectures.

The CSI driver for PowerMax supports FBA devices via Fibre Channel and iSCSI. There is no support for CKD devices, which require code changes.

Support disclaimer

Dell officially supports the published image and binary (through GitHub tickets, Service Requests, and Slack), but not custom builds.

Happy dabbling on IBM Z !

Sources