Identifying SAN disk usage using WMI – Powershell – Script of the Day

So I was commissioned with identifying the amount of actual disk space used by a bunch of Microsoft Servers that were attached to various SANs on our network. Unfortunately, despite us having a rather expensive vendoir supplied product for doing this reporting, the vendor product(s) is/are dependent on agents running on the servers to actually report back what the performance stats look like.

I fugured that the information must be accessible via WMI so I set about trying to identify something that identified disks as being remote / SAN attached.

I had a crack using several different WMI classes, thinking that I may need to tie the results from a hardware based query to identify physical disks, against the results of something like the win32_logicaldisk class – but was drawing a blank.

to identify similarities / differences betwen hosts I decided to just spit our the results of the Disk / Volume classes for a handful of hosts

I tried the following classes:
win32_logicaldisk
win32_DiskDrive
Win32_Volume

After interrogating a few hosts (some SAN attached, some not . I noticed a similarity in the device IDs returned in the following class win32_Volume.

you see all of our servers are set to have local disk for the C: and CDROM for the Z: (so I had a control group)
Executing the following however . . against a LONG list of server seemed to always return C: and Z: with device IDs in the format:

\\?\Volume{xxxxxxxx-xxxx-xxxx-xxxx-806e6f6e6963}\

Now I have looked around for an explanation as to why all the Local Disks and Local CD Roms appear with tat number at the end, but I can find no confirmation – but I figured I’d simply create a PowerShell script using this snippet of info to generate the report I require.

First of all, the wmi query that I would need :
gwmi -ComputerName <servername> -class win32_volume | select deviceid, driveletter

Now all I need to do is contruct a method to repeat the above and churn out a nice Excel style report to show disk utilisation . .

Here is the result

Function get-sandisks ([string]$InputFilename,[string]$OutputFilename)
{
$servers = gc $InputFilename

$MyObj = @()
# Cycle through the servers in the file
foreach ($server in $servers)
{Write-Host $server -ForegroundColor Green
# first test if we can ping the server (quicker than trying WMI straight away)
If (Test-Connection $server -Count 1)
{
if (Get-WmiObject -ComputerName $server Win32_LogicalDisk -ea 0)
{$disks = gwmi -ComputerName $server -class win32_volume | ?{$_.driveletter} #| ?{$_.deviceid -notmatch "806e6f6e6963"} #| select deviceid, driveletter
If ($disks)
{foreach ($disk in $disks)
{
$rep = "" | select "Server Name", "Drive Letter", "Disk Space", "Used Space", "Free Space", "DeviceID", "Type"
$Rep."Server Name" = $server
$Rep."Drive Letter" = $disk."driveletter"
$Rep."Disk Space" = $disk | %{$_.Capacity}
$Rep."Free Space" = $disk | %{$_.Freespace}
$Rep."Used Space" = $Rep."Disk Space" - $Rep."Free Space"
If ($disk.deviceid -notmatch "806e6f6e6963"){$rep.Type = "SAN"}
Else
{$Rep.Type = "Local"}
$Rep."DeviceID" = $disk | %{$_.deviceID}
Write-Host $rep
$MyObj += $Rep
$rep = $null
}
}
}
Else
{
$rep = "" | select "Server Name", "Drive Letter", "Disk Space", "Used Space", "Free Space", "DeviceID", "Type"
$Rep."Server Name" = $server
$Rep."Drive Letter" = "WMI"
Write-Host $rep "WMI" -ForegroundColor Yellow
$MyObj += $Rep
$rep = $null
}
}
Else
{              $rep = "" | select "Server Name", "Drive Letter", "Disk Space", "Used Space", "Free Space", "DeviceID", "Type"
$Rep."Server Name" = $server
$Rep."Drive Letter" = "PING"
Write-Host $rep "PING" -ForegroundColor Yellow
$MyObj += $Rep
$rep = $null
}
}
$MyObj | sort | Export-Csv -Path $OutputFilename -NoTypeInformation
}

While I appreciate that this is  not 100% accurate, I simply wanted to report on space that is in use by the SAN and is no local disk, so the result is fit for my purpose.