Powershell Get-Disk does not show all volumes in Disk Management?

Hi experts,

  Since ransomware are more popular recently, I want to create a job to enable a volume, take a backup and then offline a volume. It should be simple use steps like below. However, I find some disks does not show in Get-Disk while it is actually activated in Disk Management. What happen? What should I do? Any alternative? Diskpart.exe?

1. Set-Disk -Number 2 -IsOffline $False

2. Backup

3. Set-Disk -Number 2 -IsOffline $True

-----------------

Microsoft Windows [Version 10.0.14393]

PS C:\Users\tp1adm> $host.version

Major  Minor  Build  Revision
-----  -----  -----  --------
5      1      14393  2395

-----------------