How to add more than 26 /dev/vdd disk devices to a VM

Vanyel · 08-08-2019, 04:26 PM

Trying to move from VirtualBox to KVM under CentOS 7. Lot of differences to get used to!
I added a .qcow disk image file to my vm with :

Code:

virsh attach-disk {machine} /mnt/disk/segment_1.qcow2 vde --cache none

and that worked fine. However, I have more than 26 disks that I want to attach (I'll chain them into an LVM inside the guest).

I realized ... what happens after I reach /dev/vdz? How do I reference more disks? I found a couple of pages that let me know the upper limit of allowable devices is FAR in excess of what I need, but none said how they are referenced. What's the nomenclature?

rknichols · 08-08-2019, 04:59 PM

The next one would be /dev/vdaa . When in doubt, you can always run lsblk in the guest. In your case, that output will be somewhat longer than for most of us.

Vanyel · 08-09-2019, 08:05 AM

Great! Thanks! Now I see how to enumerate them for a script.

Hmmmm ... instead of having a script manually spell out vdf, vdg, etc, etc, is there a way to specify "next available free vd device"?

syg00 · 08-09-2019, 08:29 AM

Isn't that what scripting was invented for ?.

Vanyel · 08-09-2019, 11:31 AM

Sure ... when you HAVE to "invent the wheel", but always best to check if you're just "reinventing the wheel" first. ;-)