Plesk for Linux
kb: bug
ABT: Group A
Applicable to:
- Plesk for Linux
Symptoms
-
pmm-rasprocess produces high CPU load:
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Plesk scheduled backup is in progress
Cause
Backup process intensively uses disk subsystem which might result into high load on servers. There is a request to optimize and improve backup process in the future: #PPPM-6758
Resolution
Since Plesk Obsidian 18.0.26 there is a possibility to set priority for backup processes. Go to Tools & Settings > Backup Manager (under “Tools & Resources”), click “Settings” and look for the “Run scheduled backup processes with low priority” and “Run all backup processes with low priority” options.
Note: Use faster hard disk, SSD-disk or RAID-massive, or arrange subscriptions between several hardware nodes.
Comments
7 comments
For those as confused as I was when researching the process pmm_ras process this a related thread is here in the forum -
https://talk.plesk.com/threads/pmm-ras-wont-stop-until-its-killed.321434/
Indicates this process is actually linked to Plesk migration manager.
I'd recommend checking /var/log/plesk/PMM/migration.log to see what it's up-to, in my case the CPU load wasnt super high, but had been runnign for a while and that's what was suspect - however since this is linked to the backup process helps explain that this is most likely normal behaviour - in my case CPU wasnt as high as illustrated here but it was one of the top processes for many hours.
Hello!
Thank you for sharing you experience.
I've had my share of this problem as well. While backup compression was active I had extremely high CPU that would prevent sites from loading. After switching it off I ended up with high I/O usage at periods which would slow them down. I'm on a powerful VPS however the CPU and DISK usage was very high. Even on a dedicated server the performance drop is noticeable while pmm-ras is running. I was told by support to monitor this thread here.
I've added a suggestion in plesk uservoice regarding backup priorities which should help.
https://plesk.uservoice.com/forums/184549-feature-suggestions/suggestions/35027743-better-backup-priority-settings-to-include-nice-an
I'm hoping more people will vote on that
Currently I've had to use 3 separate cron jobs to lower the cpu and I/O priority of backups
Sorry, but the advice regarding hardware upgrades does not help with traditional hosting providers. Also, given the fact that only the Plesk version has changed (nothing else), it is rather Plesk that should be fixed! And btw, it would help if the cause is explained a bit more in detail... Any other workaround?
Since version 18.0.26 it is possible to define priority for the backup processes, please try to adjust settings under Tools & Settings > Backup Manager (under “Tools & Resources”), click “Settings.
Anton Maslov sad thing: I already did so and the problem appears even though the lowest possible priorities are already selected.
Has anyone been able to beat this issue? I already tried everything I could, but still the server crashes for 5 minutes during the backup.
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