[ironic] [tripleo] RFC: lzma vs gzip for compressing IPA initramfs
mark at stackhpc.com
Mon Nov 30 09:10:30 UTC 2020
On Fri, 27 Nov 2020 at 17:37, Arne Wiebalck <arne.wiebalck at cern.ch> wrote:
> I did a quick test (one data point):
> - the image build time increased by 10 mins
> (on a VM, this is more than double compared to gzip)
> - but: the resulting image size is ~30% smaller (421 vs 297 MB)
> - the cleaning time (unpacking on bare metal!) increased by ~30 seconds
30 seconds is a long time, even for bare metal. 134 MB is roughly to a
gigabit of network traffic. So really this comes down to how much
spare capacity you have in your network to handle bursts of these
> So, lzma looks like a good option to reduce the image size which
> we had to do in our deployment already to address boot issues
> (we removed some packages).
> Keeping gzip as the default and offering lzma as an option to
> start with as suggested by Sergii seems like a good way forward.
> I also think it would be good to have someone else test as well
> to have another data point :-)
> On 27.11.20 14:00, Sergii Golovatiuk wrote:
> > Hi,
> > LZMA causes very high CPU and memory usage for creating images, leaving
> > less resources for other processes. If Ironic is running alongside with
> > other services that may cause significant impact for them. I would leave
> > gzip option as default, would introduce --lzma as well as --gzip and use
> > lzma on 5-10% of our CI resources to test how it goes. Then after a
> > significant amount of testing we could turn it on as default. Proper
> > deprecation should be applied here as well IMHO.
> > чт, 26 нояб. 2020 г. в 17:57, Dmitry Tantsur <dtantsur at redhat.com
> > <mailto:dtantsur at redhat.com>>:
> > 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
> > https://review.opendev.org/c/openstack/ironic-python-agent-builder/+/764371
> > 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.
> > Dmitry
> > --
> > Red Hat GmbH, https://de.redhat.com/ , Registered seat: Grasbrunn,
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> > Managing Directors: Charles Cachera, Brian Klemm, Laurie Krebs,
> > Michael O'Neill
> > --
> > SergiiGolovatiuk
> > Senior Software Developer
> > Red Hat <https://www.redhat.com/>
> > <https://www.redhat.com/>
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