Monthly Archives: November 2014

Getting the Free Disk Space of Remote Computers

This started out as a simple script to try to get the free space on one of my servers, but I quickly discovered that using WMI’s Win32_LogicalDisk could only give me part of the solution. The catch is that Win32_LogicalDisk doesn’t return the information about volumes that aren’t assigned drive letters. Which is a problem if what you really need to know is how close to out of space your backup disk is! Because Windows Server Backup takes total control of the backup target disk, and doesn’t mount it as a drive letter, you need to use a different WMI Class to get the information you need. After asking some friends (PowerShell MVPs ROCK!), I was pointed to Win32_Volume, which returns all sorts of information about disk volumes whether they are assigned drive letters or not.

The next issue was how to get the actual information I wanted, and then to format it so that it actually made some sense. For example:

PSH> (Get-WmiObject –ComputerName Server1 –Class Win32_Volume).FreeSpace

This doesn’t really cut it. OK, let’s try at least getting it into a table:

PSH> Get-WmiObject –ComputerName Server1 –Class Win32_Volume | ft –auto DriveLetter,Label,FreeSpace
DriveLetter Label                               FreeSpace 
----------- -----                               --------- 
C:                                            21655351296 
D:          DATA                             103541030912 
E:          EXCHANGE                          75879378944 
F:          FILES                            142417367040 
Y:          New Volume                            5500928 
            Server1 2014_10_15 10:57 DISK_03 565375053824

Well, that’s a bit more useful, but frankly, that number for the backup volume seems big, but is it 500 GB, or 50 GB? At first glance, I have no idea. And if it’s 50 GB, I’m in trouble, but if it’s 500 GB, we’re fine. So, we need to do a bit of manipulation to the output from Format-Table, and the tool for this is to create an Expression that allows you to calculate and format a result in a way that makes more sense. For this, we use an expression as the property to display. So, for example, to display that “565375053824” as Gigabytes, we use:

Get-WmiObject –ComputerName Server1 –Class Win32_Volume `
       | ft –auto DriveLetter,`
                  @{Label=”Free(GB)”;Expression={'{0:N0}’ –F ($_.FreeSpace/1GB)}}
DriveLetter Label                            Free(GB) 
----------- -----                            -------- 
C:                                           20 
D:          DATA                             96 
E:          EXCHANGE                         71 
F:          FILES                            133 
Y:          New Volume                       0 
            Server1 2014_10_15 10:57 DISK_03 527 

Now we’re getting somewhere. But what did we do? We use the @{} to tell Format-Table that we were going to use an expression to define a column of data. The Label=”Free(GB)” creates a new column header, and the Expression={“{0:N0}” –F  means we’re going to have a numeric value (including thousands separators) with no decimal values. The calculated value for the column is ($_.FreeSpace/1GB).

So we now have a useful listing of free space on the remote server. Of course, it might be even more useful to know the percentage free. No problem, for that we use the formatting expression “{0:P0}” to express the column as a percentage, and use the calculation of ($_.FreeSpace/$_.Capacity), letting PowerShell do the work of converting that to a percentage. So:

Get-WmiObject –ComputerName Server1 –Class Win32_Volume `
       | ft –auto DriveLetter,`
                  @{Label=”Free(GB)”;Expression={“{0:N0}” –F ($_.FreeSpace/1GB)}},`
                  @{Label=”%Free”;Expression={“{0:P0}” –F ($_.FreeSpace/$_.Capacity)}}
DriveLetter Label                         Free(GB)  %Free 
----------- -----                         --------  ----- 
C:                                            20      17 % 
D:          DATA                              96      48 % 
E:          EXCHANGE                          71      71 % 
F:          FILES                             133     18 % 
Y:          New Volume                        0       58 % 
            Server1 12014_10_15 10:57 DISK_03 527     51 % 

Now we almost have it. Next, it would probably be useful to get the total capacity of the disk while we’re at it, and since I have more than one server, we should probably plan on passing this whole thing an array of computer names. So, the final script, at least for this first pass:

# ********************************************* 
# ScriptName: Get-myFreeSpace.ps1 
# Description: Script to get the free disk space
#            : on a remote computer and display it usefully
# ModHist: 26/11/2014 - Initial, Charlie
#        : 
# *********************************************
Param ([Parameter(Mandatory=$False,Position=0)]
         [String[]]$ComputerName = "Server1")
Write-Host ""
ForEach ( $Name in $ComputerName ) {
   Write-Host "Disk Utilization for server $Name is: "
   Get-WmiObject  -ComputerName $Name -Class Win32_Volume `
      | Format-Table  -auto `
            Expression={"{0:N0}" -f ($_.FreeSpace/1GB)};`
         @{Label="% Free";`
            Expression={"{0:P0}" -f ($_.FreeSpace / $_.Capacity)};`
            Expression={"{0:N0}" -f ($_.Capacity / 1GB)};`
         @{Label="Volume Label";`

You’ll see I tweaked the formatting to right align the calculated expressions, and gave my volume label column some extra space to improve readability. The result is:

PSH> Get-myFreeSpace.ps1 –ComputerName “Server1”,”Server2”
Disk Utilization for server Server1 is:
 Drive Free(GB) % Free Size(GB) Volume Label 
----- -------- ------ -------- ------------ 
   C:       20   17 %      120 
   D:       96   48 %      200 DATA 
   E:       71   71 %      100 EXCHANGE 
   F:      133   18 %      750 FILES 
   Y:        0   58 %        0 New Volume 
           527   51 %    1,024 Server1 2014_10_15 10:57 DISK_03 
Disk Utilization for server Server2 is:
Drive Free(GB) % Free Size(GB) Volume Label 
----- -------- ------ -------- ------------ 
             0   25 %        0 
   D:    1,697   53 %    3,214 Data 
   C:      484   95 %      512