One common administrative task is to find the  available disk space on a server.  The standard methods to do this are connecting to the computer remotely to verify disk space, and using VBScript scripting to gather the data.  But there is a better way…

With Powershell’s extensive use of WMI and the “piping” options, a very useful one-liner can be used to retrieve the disk space for one or more servers.

Here is the WMI property that we will be using: Win32_LogicalDisk.

To find the disk space available for one computer you would use this one-liner:

get-wmiobject Win32_LogicalDisk -computername Server001 | select __server, Name, Description, FileSystem, @{Label=”Size”;Expression={“{0:n0} MB” -f ($_.Size/1mb)}}, @{Label=”Free Space”;Expression={“{0:n0} MB” -f ($_.FreeSpace/1mb)}} | out-gridview -Title “Disk Space Scan Results”

Lets take a look at the different sections of that one-liner.

get-wmiobject Win32_LogicalDisk -computername Server001 |

This is the standard cmdlette for accessing WMI in Powershell.  The number of available WMI classes is quite extensive.  In the above example, -computername would be followed by a valid computer name. The output of that is piped  into the  Select-Object cmdlette.

select __server, Name, Description, FileSystem, @{Label=”Size”;Expression={“{0:n0} MB” -f ($_.Size/1mb)}}, @{Label=”Free Space”;Expression={“{0:n0} MB” -f ($_.FreeSpace/1mb)}} |

Select-Object, in this one-liner aliased as select, allows us to choose which properties of the returned query we want to use.  By default the Win32_LogicalDisk class provides us with the following properties:

DeviceID     : C:

DriveType    : 3

ProviderName :

FreeSpace    : 10997723136

Size         : 21478666240

VolumeName   : C_Drive

We do two things differently with our one-liner. First we grab an extra property that is always available, but not always needed.  We are requesting the “__server” property.  This will be useful when we put everything in columns later on, and really useful when we are asking for the disk space on multiple servers.

The second thing we are doing differently is to apply formatting to the “Size: Property and “Free Space” property. If you notice above the output is in bytes.  We are use to thinking of hard drives in MB or GB, not bytes.  That is way too weird.  So we are going to created two calculated properties.  There is a calculated property for “freespace” and “size”.

The calculated property is much simpler than it might first appear. To specify a calculated property we need to create a hash table; that’s what the @{} syntax does for us.  Inside the curly braces we specify the two elements of our hash table: the property Label (in this case Size or Free Space) and the property Expression (that is, the script block we’re going to use to calculate the property value).  The Label property is easy enough to specify; we simply assign a string value to the Name, like so:

Label=”Size” and Label=”Free Space”

And, believe it or not, the Expression property (which is separated from the name by a semicolon) isn’t much harder to configure; the only difference is that Expression gets assigned a script block rather than a string value:

Expression={“{0:n0} MB” -f ($_.Size/1mb)}} and Expression={“{0:n0} MB” -f ($_.FreeSpace/1mb)}} are the expressions we are using.  So what actually is going on here?

Using .NET to Format Numbers in Windows PowerShell

Powershell doesn’t have any built-in functions or cmdlettes for formatting numbers. But that’s OK; we don’t need any built-in functions or cmdlettes. Instead, we can use the .NET Framework formatting methods.

The heart-and-soul of our command is this little construction: “{0:N0}”. That’s a crazy-looking bit of code to be sure, but it’s also a bit of code that can easily be dissected:

The initial 0 (That’s a zero)  (the one that comes before the colon) represents the index number of the item to be formatted. For the time being, leave that at 0 and everything should work out just fine.

The N represents the type of format to be applied; in this case, the N is short for Numeric. Are there other types of formats we can apply? Yes there are, and we’ll show you a few of those in just a moment.

The second 0 (the one after the N) is known as the “precision specifier,” and, with the Numeric format, indicates the number of decimal places to be displayed. In this case we don’t want any decimal places, so we set this parameter to 0. Suppose we wanted to display three decimal places? No problem; this command takes care of that: “{0:N3}” -f $a. Run that command and you’ll end up with output that looks like this: 19,385,790,464.000.

That’s about all we have to do; after specifying the format type we tack on the –f (format) parameter, then follow that by indicating the value we want to format $_.FreeSpace and $_.Size.

In our one-liner we are dividing the number variables $_.size and $_.freespace by the Powershell constant mb. We could do kb or gb as well. It depends what output you want to see.

For a more extensive discussion on .net formatting, please go here:

http://technet.microsoft.com/en-us/library/ee692795.aspx

http://msdn.microsoft.com/en-us/library/dwhawy9k.aspx

This is the source I used for much of this information.

The final section of the one-liner outputs the results to the Out-Gridview window.  I have modified the “title” property so that it shows what we are attempting to do with the query.

| out-gridview -Title “Disk Space Scan Results”

 

The above information details how to find the disk space for one server.  Because the “computername” property of the Get-WmiObject cmdlette will accept an array, or a single string.  This allows us to check mutiple servers with the same one liner.  This can be done two ways.

In the first method, the computer names can be directly type into the one liner:

get-wmiobject Win32_LogicalDisk -computername server1, server2, server3

In the second method the computer names can be read from a test file using the get-content cmdlette.

get-wmiobject Win32_LogicalDisk -computername (Get-Content c:\temp\computers.txt) `

select __server, Name, Description, FileSystem, @{Label=”Size”;Expression={“{0:n0} MB” -f ($_.Size/1mb)}},`

@{Label=”Free Space”;Expression={“{0:n0} MB” -f ($_.FreeSpace/1mb)}}`

| out-gridview -Title “Disk Space Scan Results”

I prefer the second method because you can gather the disk information on many servers very quickly.

Please let me know if you have any questions about this procedure.  I would be glad to explain anything, or answer any questions.

Thanks,

Patrick