Mythics Blog

UEK vs RHCK Kernels. What do I pick?

Posted on March 8, 2022 by Erik Benner

Tags: Oracle, Oracle Linux, Kernel

When customers deploy Oracle Linux, there is often some confusion about the Kernel. Unlike Red Hat Linux, Oracle Linux gives the customer a choice for what Kernel to run.

What’s a Kernel? The Kernel is the engine of the Linux distribution, at its heart it is Linux. The Kernel powers the distribution, runs all processes, manages I/O and provides the low-level systems calls that provide security for the processes. 

Think of the Kernel as the engine of the operating system. When you have a good engine, the car can speed along the road fast and be reliable. When the engine is old, you have more maintenance and slower performance.  But you also must look at the engine, and if it fits in your model. 

There are two choices of Kernels with Oracle Linux. The first choice is the Unbreakable Enterprise Kernel (UEK), which Oracle optimizes, and the second choice is Red Hat Compatible Kernel (RHCK) which is identical to what ships with Red Hat Linux 7 and 8. You are not locked into either Kernel , a simple reboot and you can change Kernels, leaving everything else the same! Same applications, libraries, users, everything other than the Kernel!

The UEK Kernel is built on the Linux 5 kernel, with modern and up-to-date technology and includes the latest technologies like WireGuard. With RHCK, you can be on the Linux 3 or Linux 4 based Kernel which can be based on over ten-year-old technology. Before you jump and say UEK always, keep in mind not all applications are certified for the UEK Kernel. Some applications are not ready for a modern Kernel and may need to run on a Linux 3 or Linux 4 based Kernel. However, with Oracle Linux, you have a choice, a modern kernel with all the performance it brings or an older Kernel required by your application.

Speaking of performance, here is a quick example. Using sysbench, a common Linux tool, I ran a quick storage benchmark with UEK;


And then I rebooted the system, and ran the same test with RHCK;


Based on the numbers from a quick test, the UEK Kernel performed 16% better when looking at the MiB/s throughout. Imagine your database, Oracle, Postgres, MySQL, Hadoop, etc., running 16% faster by just changing the Kernel! And that is just one example!

To learn more about what Kernel is suitable for your workloads, join our Webinar on March 31st. You can register for it here.


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