You can monitor your servers filesystem with the PowerShell data provider in exMon. This tutorial explains how to monitor disk space on your server and sends an email when it falls below some threshold. 

Steps 

1. Create a new Query in exMon Administrator by right clicking the Tests folder 

2. Select the PowerShell data provider 

3. Add the following PowerShell script to the Query window:

$computer_name = "machinename"
$limit_gb = 20
$limit_bytes = $limit_gb*1024*1024*1024

$exMonResult = Get-WmiObject Win32_LogicalDisk -ComputerName $computer_name -Filter "DeviceID!='A:' and FreeSpace<$limit_bytes"   | Select-Object  @{Name="Computer";Expression={$computer_name}},DeviceID,@{Name="Size GB";Expression={$_.Size / 1GB}},@{Name="Free GB";Expression={$_.FreeSpace / 1GB}} | exMon-Out-DataTable

4. Edit the two variables, specifying the server name and the free space limit.  Monitor multiple servers To monitor multiple servers, you can use a PowerShell script with query parameters and Object Groups. 

Steps 

1. Replace the first line in the Query with:

$computer_name = "{@computer_name[default:localhost][datatype:string][preview:localhost]}"

2. Create an object group and add the query to the object group, once for each server to monitor 

3. Add Extra Parameters to each query to specify which server to monitor:

--@computer_name es-srv-01

    Example when monitoring two servers.