[ironic] [tripleo] RFC: lzma vs gzip for compressing IPA initramfs
arne.wiebalck at cern.ch
Mon Nov 30 09:22:56 UTC 2020
On 30.11.20 10:10, Mark Goddard wrote:
> 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
From what I understand the main issue Dmitry is trying to address
with this proposal is to reduce the risk of (UEFI) boot issues due
to memory constraints on the target host.
>> 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:
>>> 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
>>> 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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