Kubernetes – Run workloads on the Control Plane Node

If you ever installed a Kubernetes cluster, you probably know that the minimal setup is composed of 2 nodes: a Control Plane Node (previously called master) and a Worker Node. This is a good thing as we usually don’t want workloads interfering with the API in production environments.

But what about lab environments where you want to run everything in a single VM for example? Well, it’s absolutely possible and actually very simple to configure a Control Plane Node to also accept workloads (pods).

This is managed by “taints”, which is a configuration string applied to nodes. On your Control Plant Node, you can see this by running:

# kubectl describe nodes YourNodeName | grep Taints

It will give you back a string resembling “node-role.kubernetes.io/master:NoSchedule”. NoSchedule, the name says it all.

Well, you can simply remove this taint by running the following command, note the “-” at the end to remove the taint:

kubectl taint nodes YourNodeName node-role.kubernetes.io/master:NoSchedule-

And that’s it, you can now run workload pods on your Control Plane Node in your lab.

CentOS Stream 8 software RAID1 and UEFI GPT Boot configuration

This post has nothing to do with the usual content of this website (not K6 related) but I’m sharing my experience of configuring a CentOS Stream 8 Linux software RAID 1 installation on an UEFI system that actually boots when you replace a failed disk.

Most of the tutorials and articles online are about such installations where the the disks are in MBR (legacy) mode and not GPT (UEFI) and this has a huge impact on how your system boots and how you act when a disk fails. We’ll have a look at a scenario where we:

  • Start by installing CentOS Stream 8 in software RAID 1 (on 2 disks) mode
  • Simulate the failing of one drive
  • Replace the drive so the RAID arrays are synchronized again
  • Configure the UEFI to be able to boot on this new replacement drive

For demonstration purposes, this will be done using a VM in VirtualBox, but it also applies to any PC or Server booting in UEFI mode, as most machines do nowadays.

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Gigabyte GA-5AX performance optimisation

Having my working K6 system since a couple of weeks now I began tweaking the BIOS settings for my Gigabyte GA-5AX rev 4.1 to find the best performance, as it took quite some testing I’m now sharing what I found ;)

First of all let’s remember the system:

  • AMD K6-2+ 550 MHz
  • 768 MB PC133 CL2  RAM
  • nVidia GeForce 3 Ti200 64MB
  • Fast SATA HDD
  • Windows XP SP3

I began by setting reasonably good BIOS settings and after each individual setting change I  ran a series of 5 benchmarks using the good old Quake 3 v1.32 with “timedemo 1, demo four”. Quake 3 has the advantage of giving very consistent and reproducible results over any other benchmark tool and after all I’m using this system for old games…

The first tests I made is not BIOS related though…I tried to find the best nVidia driver working with my card. The 23.01 gave me an average of 28 FPS and the 21.83 WHQL an average of 28.7 FPS so there is the first base…I’ll be using the ForceWare 21.83 WHQL for the rest of the tests.

Now I’ll go trough each BIOS setting and give the fps change from this baseline…note that the changes are “incremental” by always keeping the previous test’s best performance.

Primary Frame Buffer

  • 2 MB (BIOS default): 28.7 FPS
  • All: 28.2 FPS
  • Disabled: 28.8 FPS

VGA Frame Buffer

  • Enabled: 28.8 FPS
  • Disabled: 27.7 FPS

Data Merge

  • Enabled: 28.8 FPS
  • Disabled: 27.7 FPS

Tweaking “IO Recovery Period” or “AGP Texture Size” didn’t change anything. Then I changed the CPU from an AMD K6-2+ 550MHz to an AMD K6-3+ 550 MHz to see how the 128kB additional L2 cache influenced the result. Well the fps jumped from 28.8 to 31.1 FPS which is nice!

As you can see I wasn’t that wrong with my default configuration as I only managed to “lower” the result by tweaking some settings…that’s experience talking ;) Here are the pictures of my final best result settings…

GA-5AX BIOS – Base Menu

GA-5AX BIOS – Power Management Setup

GA-5AX BIOS – PNP/PCI Configuration

GA-5AX BIOS – Integrated Peripherals

GA-5AX BIOS – BIOS Features Setup

GA-5AX BIOS – Chipset Features Setup

K6-2+ 550 MHz OS Boot Speed

A quick video which shows the boot speed on an AMD K6-2+ 550MHz, 768 MB RAM and SATA disk system for Windows XP and Ubuntu 10.04. Bot operating systems are “stock” with the latest updates installed and no special optimisation has been done.

As you can see, you are much better off using Windows XP on a K6 machine as the Linux distributions with GUI are terribly slow on this hardware.

It’s not only the boot process which is slow on Linux but also the whole OS GUI (Gnome in this case) which feels awfully slow to the point where it’s unusable; Windows XP on the other hand is quick and snappy!

So the common myth that Linux is faster than Windows on old hardware isn’t so true here…