Kubernetes on Z with PowerMax: Modern Software Running on Mainframe
Mon, 02 Oct 2023 13:21:45 -0000
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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 I were talking about the financials of the platform, I would evaluate the total cost of ownership (TCO) alongside various IT solutions and the value deduced thereof. If discussing existing technical pain points, I would evaluate technical 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 installing 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 I had not originally thought of. More specifically:
- Physical server consolidation – I’ll create a plethora of virtual servers when needed
- License Consolidation – Certain applications with x86 were licensed on a per engine basis. A quad core x86 server may need four application licenses to function. I needed one license for my Linux on Z environment (at the time of testing)
- Scalability – I could scale horizontally by adding more virtual machines and vertically by increasing the network ports accessible to the server and adding more memory/storage
- Reliability – Mainframe technology has been known to be reliable, utilizing fault tolerant mechanisms within the software and hardware to continue business operations
With the 2023 addition of Kubernetes on LinuxOne (mainframe that only runs Linux), you can scale, reduce TCO, and build that hybrid cloud your IT management requires. With Kubernetes providing container orchestration irrelevant of the underlying hardware and architecture, you can leverage the benefits of LinuxOne to deploy your applications in a structured fashion.
Benefits when deploying Kubernetes to Linux on Z may include:
- Enablement of DevOps processes
- Container Scalability – using one LinuxOne box with hundreds (if not thousands) of containers
- Hybrid Cloud Strategy – where LinuxOne is servicing various internal business organizations with their compute and storage needs
With Dell providing storage to mainframe environments with PowerMax 8500/2500, a Container Storage Interface (CSI) was created to simplify your experience with allocating storage to Kubernetes environments when using Linux on Z with Kubernetes.
The remaining content will focus on the CSI for PowerMax. Continue reading to explore what’s possible.
Deploy Kubernetes
Linux on IBM Z runs on s390x architecture. This means that all the software we use needs to be compiled with that architecture in mind.
Luckily, Kubernetes, CSI sidecars, and Dell CSI drivers are built in Golang. Since the early days of Go, the portability and support of different OS and architectures has been one of the goals of the project. You can get the list of compatible OS and architecture with your go version using the command:
go tool dist list
The easiest and most straightforward way of trying Kubernetes on LinuxOne is by using the k3s distro. It installs with the following one-liner:
curl -sfL https://get.k3s.io | sh -
Build Dell CSI driver
The Dell CSI Driver for PowerMax is composed of a container to run all actions against Unisphere and mount a LUN to a pod, with a set of official CSI sidecars to interact with Kubernetes calls.
The Kubernetes official sidecars are published for multiple architectures including s390x while Dell publishes only images for x86_64.
To build the driver, we will first build the binary and then the image.
Binary
First, let’s clone the driver from https://github.com/dell/csi-powermax in your GOPATH. To build the driver, go in the directory and just execute:
CGO_ENABLED=0 GOOS=linux GOARCH=s390x GO111MODULE=on go build
At the end of the build, you must have a single binary with static libs compiled for the s390x:
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 minimal Red Hat Universal Base Image. There is no s390x compatible UBI image. Therefore, we need to rebuild the container image from a Fedora base-image.
The following is the Dockerfile:
# Dockerfile to build PowerMax CSI Driver
FROM docker.io/fedora:37
# dependencies, following 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"]
We can now build our container image with the help of docker buildx, which makes building cross-architecture a breeze:
docker buildx build -o type=registry -t coulof/csi-powermax:v2.8.0 --platform=linux/s390x -f Dockerfile.s390x .
The last step is to change the image in the helm chart to point to the new one: https://github.com/dell/helm-charts/blob/main/charts/csi-powermax/values.yaml
Et voilà! 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’s easy to build and utilize them for many different architectures.
The CSI driver for PowerMax supports FBA devices via Fiber Channel and iSCSI. There is no support for CKD devices which require code changes.
The CSI driver for PowerMax allows CSI-compliant calls.
Note: Dell officially supports (through Github tickets, Service Requests, and Slack) the image and binary, but not the custom build.
Useful links
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Authors: Justin Bastin & Florian Coulombel