I need to do
FREE PLACE ON DISC O: ({ITEM.LASTVALUE}) FROM (total disk space)
Trigger expression
{sql01:vfs.fs.size[O:,free].last(0)}<21474836480
Thanks in advance!
Assuming you need to see the used/total space in the trigger title, there's no need to put that information in the trigger itself: starting from Zabbix 4.4, it's available as an optional information/column in the Problems page:
It's "none" by default, but can be selected separately or within problem name:
The part highligthed in green is added:
See the documentation for: operational_data_of_problems