[ironic] [tripleo] RFC: lzma vs gzip for compressing IPA initramfs

Dmitry Tantsur dtantsur at redhat.com
Thu Nov 26 16:54:53 UTC 2020

Hi folks,

I've been playing with ways to reduce the size of our IPA images. While
package removals can only save us tens of megabytes, switching from gzip to
lzma reduces the size by around a third (from 373M to 217M in my testing).

What's the caveat? The unpacking time increases VERY substantially. On my
nested virt lab the 217M image took around 5 minutes to unpack. I'm not
sure how much it will impact real bare metal, please feel free to test
and tell me.

So, what do you think? Switching to lzma by default will likely affect CI
run time (assuming we still have DIB jobs somewhere...) and development
environments, but it will also provide a visible reduction in the image
size (which benefit all environments). Large TripleO images may
particularly benefit from this (but also particularly affected by the
unpacking time).

Feedback is very welcome.


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