Feature Overview (aka. Goal Summary)  

Currently RHCOS boot images are compressed using gzip which is generally outmoded by zstd and xz in both terms of compression ratio and speed. While xz offers marginally better compression ratio zstd is better with regard to speed in both compression and decompression. Therefore we'd like to utilize zstd which is widely supported and includes tools in RHEL8 and later.

Goals (aka. expected user outcomes)

Compress RHCOS boot media using zstd, Download and decompress as appropriate in all places that currently decompress boot images

Requirements (aka. Acceptance Criteria):

• RHCOS Pipeline for RHCOS 10 compresses boot images using zstd
• RHCOS Pipeline compression stage is at least as fast as the current `gzip -6` method and compresses better than gzip
• Installer and other tools which decompress boot images handle zstd

Anyone reviewing this Feature needs to know which deployment configurations that the Feature will apply to (or not) once it's been completed.  Describe specific needs (or indicate N/A) for each of the following deployment scenarios. For specific configurations that are out-of-scope for a given release, ensure you provide the OCPSTRAT (for the future to be supported configuration) as well.

Use Cases (Optional):

Questions to Answer (Optional):

Out of Scope

Background

Customer Considerations

zstd may not exist everywhere that gzip does today but it's readily available and we expect the tools we provide to handle decompression for them, such as openshift-install{}

Documentation Considerations

Interoperability Considerations