RHEL VM not seeing extra disk

[serged]

Hi,

I have a RHEL 6.2 64-bit VM running in Proxmox 1.9 to which I've added an extra 2TB disk, using the VIRTIO bus. The VM is running on the KVM hypervisor.

However, after adding the disk, restarting the VM and logging in through the console, I am unable to see the disk under /dev. The original disk, from when I created the VM is there under /dev/vda, but there's no /dev/vdb. I can confirm that when I log onto the host, the disk is definitely there and taking up all of the space.

I've tried attaching it using IDE and SCSI as well (although I didn't reboot), but it still refuses to detect the new disk.

Has anyone come across this problem before? How can I get the VM to "detect" the new disk? Is this an issue with RHEL more than Proxmox?

Thank you

 

[ahe]

Did you remember to turn off the machine (not just reboot) after you added the disk?

Best regards

 

[serged]

Thanks for that ahe. Shutting the VM down and then bringing it up instead of rebooting worked, although I'm not sure why as I thought it was essentially the same thing.

 

[m.ardito]

I think it's almost the same thing in "real" machines (there is the concept of cold boot (or hard boot) and warm boot, see http://support.microsoft.com/kb/102228/en-us)

Virtual machines (at least in pve) can't detect "virtual hardware" changes without a "virtual cold boot".
with "real" machines, you can't switch the hardware while the're running and simply reboot to make them see it. You likely break electronics that way :-D

hth, Marco