Red Hat Engineering is planning to convert the Red Hat Tuning Brief, Optimizing SAS on Red Hat Enterprise Linux (RHEL) 6 & 7 Version 1.3 (optimizingsasonrhel6and7_2.pdf), to cover RHEL Versions 7 through 10.
Until the official new guidelines are complete and ready for distribution, we will note the
following interim advice for RHEL Tuning and Configuration for All RHEL Versions 7 through 10.
RHEL 7, 8, 9, &10 – Common Advice to All RHEL Versions
For RHEL Versions 7,8, 9, and 10, the tuning and configuration from the RHEL 6&7 Tuning Guide, will be the Same – With the exception of the RHEL 8 Swappiness Algorithm Changes Noted in the RHEL 8 Section below. Tuning and configuration for RHEL 8, 9 and 10 will remain the same as RHEL 7, with the following informational notations:
- The IO Elevator selections that default in RHEL 8 are the Same recommended in RHEL 7, but have undergone Name Changes:
- The DEADLINE elevator recommended for use in RHEL 6 & 7 for non-FLASH IO devices, is now called the mq-deadline elevator, and is still recommended.
- The NOOP elevator recommended for use in RHEL 6 & 7 for FLASH IO Devices, is now called the none elevator, and is still recommended.
- The new elevators in RHEL 8, 9, and 10 designated as Kyber, and BFQ (replacing CFQ) are Not to be used with SAS 9 or SAS Viya.
- The Power Management, tuned, udev, ulimits, and multipath advice will remain the same. Please note that while the tuned files can remain in their current RHEL 7 location and still function, the official ongoing default location for RHEL 8, 9, and 10 tuned files will change.
- The advice in Section 2.3.1.1 Concatenated vs. Striped Logical Volumes, will be updated. For HDD Monolithic Storage sub-systems it will still apply. For high speed ALL FLASH Storage systems, it is still helpful for performance to follow this advice. Please note that Single LUN Logical Volumes can provide adequate performance as long as the volume consists of multiple SSD drives. This is dependent on the specific All Flash storage models and drives used, and their ability to offer high LUN Queue depth management. I.E., in the case of VMWare, VMDKs can be mounted as single LUN LVs on high-speed Flash Storage.
RHEL 8 Specific Changes – Departure from the Other RHEL Versions
The configuration and tuning for RHEL 8 will follow the same RHEL 7 specific guidelines as posted in the current RHEL 6 & 7 Document and as noted above. The following RHEL 8 Specific exception is provided.
- There were new and significant changes in the RHEL Swappiness Algorithm settings in RHEL 8 from the previous defaults in RHEL 7. This caused undesirable premature swapping of anonymous memory, affecting the virtual memory usage and performance of many RHEL 8 systems. These changes were reverted to their old RHEL 7 defaults, beginning RHEL 9 and forward, to correct the problem. RHEL 7, 9, and 10 require NO Swappiness algorithm tuning change. RHEL 8, however does. Please review the following blog to learn about, tune, and configure for those changes in RHEL 8 ONLY:
Red Hat RHEL 8 Release Swappiness Algorithm Setting Requires Change - SAS Support Communities
If there are any questions/concerns about interim advice, please open a SAS Technical Support ticket for support, and liaison to the R&D CS&E Performance Team. If Red Hat support is required, they will be integrated into the conversation to open a support ticket with them.
Summary
For the most part, you can apply the RHEL 7 advice in the RHEL 6 & 7 Tuning Guideline for RHEL Versions 8, 9, & 10. If you have questions on the exceptions above, please file a Technical Support Ticket to engage the R&D CS&E Performance Team for guidance.
The RHEL 7 Tuning advice for SAS 9 is largely acceptable for SAS Viya Hosts. Please note that this advice will apply largely to the Viya Worker and Runtime Environment (Compute) nodes. Some of the advice may vary for Microservices and Controller nodes – please see your Account Team or Technical Support for any implementation specific guidelines for your planned workload.
