[openstack-dev] Disk space requirement - any way to lower it a little?

Cédric Jeanneret cjeanner at redhat.com
Fri Jul 20 07:49:27 UTC 2018

On 07/19/2018 06:55 PM, Paul Belanger wrote:
> On Thu, Jul 19, 2018 at 05:30:27PM +0200, Cédric Jeanneret wrote:
>> Hello,
>> While trying to get a new validation¹ in the undercloud preflight
>> checks, I hit an (not so) unexpected issue with the CI:
>> it doesn't provide flavors with the minimal requirements, at least
>> regarding the disk space.
>> A quick-fix is to disable the validations in the CI - Wes has already
>> pushed a patch for that in the upstream CI:
>> https://review.openstack.org/#/c/583275/
>> We can consider this as a quick'n'temporary fix².
>> The issue is on the RDO CI: apparently, they provide instances with
>> "only" 55G of free space, making the checks fail:
>> https://logs.rdoproject.org/17/582917/3/openstack-check/legacy-tripleo-ci-centos-7-ovb-3ctlr_1comp-featureset001-master/c9cf398/logs/undercloud/home/zuul/undercloud_install.log.txt.gz#_2018-07-17_10_23_46
>> So, the question is: would it be possible to lower the requirment to,
>> let's say, 50G? Where does that 60G³ come from?
>> Thanks for your help/feedback.
>> Cheers,
>> C.
>> ¹ https://review.openstack.org/#/c/582917/
>> ² as you might know, there's a BP for a unified validation framework,
>> and it will allow to get injected configuration in CI env in order to
>> lower the requirements if necessary:
>> https://blueprints.launchpad.net/tripleo/+spec/validation-framework
>> ³
>> http://tripleo.org/install/environments/baremetal.html#minimum-system-requirements
> Keep in mind, upstream we don't really have control over partitions of nodes, in
> some case it is a single, other multiple. I'd suggest looking more at:

After some checks on y locally deployed containerized undercloud (hence,
Rocky) without real activity, here's what I could get:
- most data are located in /var - this explains the current check.

If we go a bit deeper, here are the "actually used" directory in /var/lib:
20K	alternatives
36K	certmonger
4.0K	chrony
1.2G	config-data
4.0K	dhclient
6.0G	docker
28K	docker-config-scripts
92K	docker-container-startup-configs.json
44K	docker-puppet
592K	heat-config
832K	ironic
4.0K	ironic-inspector
236K	kolla
4.0K	logrotate
286M	mysql
48K	neutron
4.0K	ntp
4.0K	postfix
872K	puppet
3.8M	rabbitmq
59M	rpm
4.0K	rsyslog
64K	systemd
20K	tripleo
236K	tripleo-config
9.8M	yum
7.5G	total

Most of the "default installer" partition schema don't go further than
putting /var, /tmp, /home and /usr in dedicated volumes - of course,
end-user can chose to ignore that and provide a custom schema.

That said, we can get the "used" paths. In addition to /var/lib, there's
obviously /usr.

We might want to:
- loop on known locations
- check if they are on dedicated mount points
- check the available disk space on those mount points.

An interesting thing in bash:
df /var/lib/docker
Filesystem     1K-blocks     Used Available Use% Mounted on
/dev/sda1      104846316 10188828  94657488  10% /

This allows to get:
- actual volume
- free space on the volume.

More than that, we might also try to figure out some pattern. For
instance, "docker" seems to be a pretty good candidate for space, as it
will get the images and container data. This is probably even the
biggest eater, at least on the undercloud - as well as the logs (/var/logs).

We might do a check ensuring we can, at least, DEPLOY the app. This
would require far less than the required 60G, and with a proper doc
announcing that, we can get a functional test, aiming on its purpose:
ensure we can deploy (so asking, let's say, 10G in /var/lib/docker, 5G
in /var/lib/config-data, 5G in /usr, 1G in /var/log) and, later, upgrade
(requiring the same amount of *free* space).

That would require some changes in the validation check of course. But
at least, we might get a pretty nice covering, while allowing it to run
smoothly in the CI.
But, as said: proper documentation should be set, and the "60G minimum
required" should be rephrased in order to point the locations needing
space (with the appropriate warning about "none exhaustiveness" and the

Would that suit better the actual needs, and allow to get a proper disk
space check/validation?



>   https://docs.openstack.org/infra/manual/testing.html
> As for downstream RDO, the same is going to apply once we start adding more
> cloud providers. I would look to see if you actually need that much space for
> deployments, and make try to mock the testing of that logic.
> - Paul
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Cédric Jeanneret
Software Engineer

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