I just uses below query in grafana panel which provides utilized percent same like expecting free,used,total sized in GB.
SELECT mean(“used_percent”) AS “used_percent” FROM “disk” WHERE (“host” = ‘node1’) AND $timeFilter GROUP BY time($interval), “path”, “device”, “fstype” fill(null)
Not sure the disk plugin gives you Free GB as such. You could
a) convert it using tick script and write it back to your measurement (field names might be off slightly)
|eval(lambda: “Free_Megabytes” / 1024.00,
lambda: “Percent_Free_Space”)
.as(‘Free_Megabytes’,‘Percent_Free_Space’)
b) change the “unit” in Grafana to use GB
A is better if you want to conver the values and use them in alert messages
B is better if you just want to conver the current value to something else.