Possible to assign disk drive letter to unassigned drives depending on size via powershell

Question

Currently spinning up 11 unallocated volumes via terraform but noticed that the volumes come in a random order on the machine and not in the specified order of the code. Trying to figure out a way to name and assign a drive letter dependent on the size of the disk via powershell

Answer 1

PLEASE NOTE: I did not test this code as I don't have a environment currently for that.

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Nonetheless, this should accomplish what you want, but may need some tweaks if you prefer a different partition style or what not.

It gets all the disks that are not online then puts them online.

Then within a loop

1. It uses MBR partition style on each disk
2. creates a new partition using the full diskspace
3. query the disk to show what size it is in GB
4. Show the disk size then prompt for the designated drive letter from user input
5. verify the drive letter is not being used and is a valid letter
6. format the drive with the letter using NTFS

# get new ebs volumes applied from terraform
$newDisks = Get-Disk | Where-Object {$_.IsSystem -eq $False -and $_.PartitionStyle -eq "RAW"}
$usedLetters = (Get-Volume).DriveLetter 

foreach ($disk in $newDisks){
    # set disk to online
    try {
        Set-Disk -Number $disk.Number -IsOffline $False
    }
    catch {
        throw "could not get disk online"
    }
    #? create partition change MBR to GBT if preferred
    try {
        Initialize-Disk -Number $disk.Number -PartitionStyle "MBR"
    }
    catch {
        throw "initialization failed"
    }
    try {
        $partition = New-Partition -DiskNumber $disk.Number -UseMaximumSize
    }
    catch {
        throw "partition failed"
    }

    # get the size to know which letter should get assigned
    $partSize = Get-Partition -PartitionNumber $partition.PartitionNumber
    $partSize = [math]::round((($partSize.size)/1GB),2)
    $size = "$partSize GB's"

    # get drive letter from user
    $driveLetter = Read-Host "Drive letter for disk that is $size"
    $letters = @("b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z")
    # check if letter is valid
    $isLetter = $null -ne ($letters | Where-Object {$driveLetter -ieq $_})
    # check if letter is already used
    if ($isLetter){
        $isLetter = $null -eq ($usedLetters | Where-Object {$driveLetter -ieq $_})
    }
    if(!$isLetter) {
        throw "invalid drive letter $driveletter"
    }

    # finally format the drive with the letter
    try {
        Format-Volume -DriveLetter $driveLetter -FileSystem NTFS -Confirm:$FALSE
    }
    catch {
        throw "format failed"
    }
}

Hope it helps, let me know if there are any issues and I can step through it. Also, there is possibility to run a similar script within terraform itself while launching the instance (user_data), but that takes a bit more leg work and might not be feasible if system is already running :)