Why can't I loop through my disk size? - powershell

Question

This is very simple code that I can't seem to make function properly
I want to find all the drives on my computer then, want to display their size.
$disks = gwmi win32_LogicalDisk | Where {$_.DriveType -eq "3"} | Select DeviceID
foreach ($i in $disks){
$i
gwmi win32_logicaldisk | Where {$_.DeviceID -eq "$i"} | Select Size
}
When displaying $i, the output is exactly as I need it I even used a Read-Host to check them one by one and every drive letter is displayed. Unfortunetly, the command to Select the size does not return anything.
Thanks for the help!

Answer 1

It would be more intuitive to me to iterate through disks themselves, not their IDs, i.e.
$disks = gwmi win32_LogicalDisk | Where {$_.DriveType -eq "3"}
foreach ($disk in $disks)
{
$disk.Size
}
$disk | Select Size also works, and, as Joey neatly complemented, whole thing is equivalent to
gwmi win32_LogicalDisk | Where {$_.DriveType -eq "3"} | Select -ExpandProperty Size

Answer 2

I don't know powershell really, but I figured I'd mess around with your script. Looks to me like the "$i" is wrong - instead use $i.DeviceID (without the quotes). Whole script that seems to work for me:
$disks = gwmi Win32_LogicalDisk | Where {$_.DriveType -eq "3"} | Select DeviceID
foreach ($i in $disks){
$i.DeviceID
gwmi Win32_LogicalDisk | Where {$_.DeviceID -eq $i.DeviceID} | Select Size
}
Another option would be to skip the iteration:
gwmi Win32_LogicalDisk | Where {$_.DriveType -eq "3"} | Select DeviceID, Size
Algorithmically I would recommend this based on execution -- the approach you are taking now iterates over all of the devices two times inside loops (basically O(n^2)). The "other option" above only iterates over them once.

Answer 3

Try to use server side filtering when ever you can using the Filter parameter instead of the Where-Object cmdlet (client side filtering), it performs faster. The latter gets ALL objects first and only then performs the filtering.
Get-WmiObject Win32_LogicalDisk -Filter "DriveType=3 AND DeviceId='$($i):'" | Select-Object Size