Add ability to manually set low space warning/auto clean trigger value

[lukaszkaluznybrag]

Is your feature request related to a problem? Please describe.

Low space warning is set to 70% and "auto-clean" to 85% of disk utilization. In case of small volumes like 10-20GB it is ok, but let say in case of 200GB we are getting notification when 60GB is free (70%) and "auto-clean" is started when 30GB is still available (15%).

In case of 400GB:

• warning <120GB
• auto-clean <60GB

Summary: bigger volumes - more unnecessary notifications and unutilized GBs due to limits.

Describe the solution you'd like

It would be nice to have a fields to configure these alert levels using GUI.

Describe alternatives you've considered

• ability to set this parameters by config file(s)
• static values but depends on volume size

[osmontero]

I think it shouldn't be a fixed percentage or a fixed size. Maybe a calculation based on the disk usage trend, warning approximately one week before the disk is expected to fill up, and start removing 24h before the time expected it will reach 100%. Always considering the default minimum free space that OpenSearch nodes must have (5G) and a margin of error.