Loop and Array of Arrays in powershell

Question

I was hoping someone could help me. I am new to powershell and struggling with trying to find the right way to approach something in my script. The script is to do a restore check on our backups using the veeam powershell commands. We have 7 backup jobs with various servers in each job and various drives being backed up in each job. Sometimes the servers are in multiple jobs as we have to split the drives across jobs as we copy the backup jobs to USB every day (so we have to balance out the amount of data we backup in each job so that we can copy the drives to the USB drives). I can write the entire script and get it to work but its around 800 lines long and is very inefficient although easy to understand for my team (and me later on!). My current approach pretty much revolves around performing certain actions for each backup job then each server within that job on each disk. I would like to cut it down using an array/loop. I have figured out how to use basic loops and arrays but I am struggling with being able to link the drives and servers in an array for example:

$Backupjob1 = "Backup Job 1E"
$Backupjob1Servers =@('Server1','Server2')

Somekind of array that allows different numbers of multiple drives for Server1 and Server 2.

$Backupjob1ServeDrives =@(Server1.Drive1 ='C', Server1.Drive2 ='F', Server2.Drive1 = 'C')

and then I need to loop through it so that on each loop, it performs an action on server1 and its first drive then does the next drive. Once server1 has finished, it performs the action on server2 on its first drive and then repeats on the second drive.

I understand the basics of looping through an array but I am struggling to understand how i would create an array of arrays that can deal with the above and then loop through it correctly.

I am stuck as not sure what array works and what options there are.

Answer 1

One way would be to externalise your config into a json file or similar and feed that to your script. Here is an example using a json string:

$serverConfig = @"
[{
    "serverName": "server1",
    "backupDrives": [
        "D","F"
    ]
},
{
    "serverName": "server2",
    "backupDrives": [
        "D","G","H"
    ]
}]
"@

$serverList = $serverConfig | ConvertFrom-Json

foreach($server in $serverList) {
  Write-Host "Server: $($server.serverName)"

  foreach($drive in $server.backupDrives) {
    Write-Host "Backing up drive $drive..."
    # Logic for the backup 
  }
}

This demonstrates handling the array of arrays you reference, you have an array of server objects and each server object has an array of drives, so on each iteration of the servers you iterate the server's drives too.

If you save the string into a config file your script could read that in, and then if you make any changes to the backup configuration you only need to change the config file and not the script.

Answer 2

It sounds like you want a dictionary type - thankfully PowerShell has a builtin unordered dictionary type called a hashtable that can be used.

In order to construct a hashtable literal, use @{...} instead of @(...):

$driveMapping = @{
    Server1 = @{
      Drive1 = 'C'
      Drive2 = 'F'
    }
    Server2 = @{
      Drive1 = 'C'
    }
}

To traverse this data structure, use a simple nested loop:

foreach($server in $drivemapping.psbase.Keys){
    Write-Host "About to backup the drives on server '$server'"
    foreach($drive in $drivemapping[$server].psbase.Keys){
        $driveLetter = $drivemapping[$server][$drive]
        Write-Host "About to backup drive '$drive' with letter '$driveLetter' on server '$server'"
    }
}