“Access is denied” trying to bring VM-attached USB hard disk back online in Disk Manager

diskmanagementhyper-v-server-2012-r2passthroughusbwindows-server-2012-r2

Windows Server 2012 R2 Hyper-V with CentOS 6.5 and CentOS 7 VMs.

  1. In Disk Manager, I right-click my USB hard drive and pick Offline.
  2. In Hyper-V Manager, I right-click either CentOS VM, and I connect the physical disk to either of the VMs as a SCSI drive. The drive is listed and connects without complaining.
  3. In Disk Manager, I right-click my USB hard drive and pick Online.
  4. I get a popup with the title "Virtual Disk Manager" and the text "Access is denied." and a red X icon and OK is my only option.

Any time after step 1, I notice that there is a little info bubble icon on the drive. Mousing over it says, "The disk is offline because of policy set by an administrator."

If after step 2 I detach the physical disk from the VM, step 3 works, I get the drive online again, but obviously this is not helpful in terms of accessing it from the VM.

Why is access denied? Is this to do with the drive not being passthrough-capable?

Best Answer

3. In Disk Manager, I right-click my USB hard drive and pick Online.

Are you doing this on the host? If so, you're doing it wrong. It needs to remain offline on the host. Setting it Online would be done from the guest, if the guest were a Windows VM. For Linux/Unix you probably need to do some kind of mount from within the guest.

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