[JIRA] (OVIRT-636) Add disks in memory for lago slaves

[Barak Korren (oVirt JIRA)]

    [ https://ovirt-jira.atlassian.net/browse/OVIRT-636?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18608#comment-18608 ] 

Barak Korren commented on OVIRT-636:
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We can also create the zram drive and do the mounts in the job code...
I think its best to let the job create and destroy things because that will ensure things get cleaned.

But - we need to ensure we keep cache directories around, so maybe we need both - move caches to RAM on host startup and write them back to disk periodically and on shut-down. And have the job workspaces be put on ram and destroyed after every run.

IIRC /var/lib/lago is the local cache directory that is bind-mounted into the Mock chroot, so that need to me moved to RAM on boot and synced back to disk.
The rest of the job I/O seems to indeed happen in /var/lib/mock and /home/jenkins so we can consider placing a ram drive there each time the job starts.
But /home/jenkins might be tricky because it may be used for other stuff (the slave binary for example), so we should probably just dynamically create a ram-drive for $WORKSPACE at the job level.

One way to move things into RAM at boot time is to use '/etc/sysconfig/readonly-root' and '/etc/rwtab', this has the benefit of making the hosts mostly stateless, but may also make changing configuration a little tricky.

> Add disks in memory for lago slaves 
> ------------------------------------
>
>                 Key: OVIRT-636
>                 URL: https://ovirt-jira.atlassian.net/browse/OVIRT-636
>             Project: oVirt - virtualization made easy
>          Issue Type: Bug
>            Reporter: eyal edri [Administrator]
>            Assignee: infra
>
> We need to try moving the Lago slaves in CI to work with memory instead of local disks,
> It might speed up the tests significantly.
> We have 2 choices:
> 1. add code to the job and mount the dir on /dev/shm/
> 2. create zram drive and mount the following dirs on it:
> # /var/lib/mock
> # /var/lib/lago
> # /home/jenkins
> Each host should have enough memory to run current tests on them,
> however we'll need to make sure to clean that drive after each run.
> Lets try it on one of the slaves to see what is the best solution before implementing for all slaves.



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