Get total and free disk space using Prometheus

Question

I try to get Total and Free disk space on my Kubernetes VM so I can display % of taken space on it. I tried various metrics that included "filesystem" in name but none of these displayed correct total disk size. Which one should be used to do so?

Here is a list of metrics I tried

node_filesystem_size_bytes
node_filesystem_avail_bytes
node:node_filesystem_usage:
node:node_filesystem_avail:
node_filesystem_files
node_filesystem_files_free
node_filesystem_free_bytes
node_filesystem_readonly

Solution 1

According to my Grafana dashboard, the following metrics work nicely for alerting for available space,

100 - ((node_filesystem_avail_bytes{mountpoint="/",fstype!="rootfs"} * 100) / node_filesystem_size_bytes{mountpoint="/",fstype!="rootfs"})

The formula gives out the percentage of available space on the pointed disk. Make sure you include the mountpoint and fstype within the metrics.

Solution 2

FS utilization can be calculated as

100 - (100 * ((node_filesystem_avail_bytes{mountpoint="/",fstype!="rootfs"} )  / (node_filesystem_size_bytes{mountpoint="/",fstype!="rootfs"}) ))