Combined alert for disk drive available space

Hi all,

I am trying to create an combined alert for available disk space but all I can get at the moment is a single alert per disk.

I have created a group alert for interfaces up/down status using a group on NPM and alerting when the group is down but a group for disk drives only alerts for up/down status and don't seem to work for disk space (or thresholds).

The alert configured at the moment is:

"Trigger Alert when all of the following apply

     Volume Percent Available is less than 30

     Volume Type is equal to Fixed Disk"

But like mentioned earlier this generates an alert per each volume.

Any ideas on how to get a combined alert?