bcache and LVM storage: Can't delete VM disk

VTOLfreak

Member
Nov 14, 2017
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If you are trying out bcache in your VM's and are using LVM storage in Proxmox, you might want to blacklist the bcache module on your host.

I use LVM over iSCSI storage for my virtual machines. I was playing around with bcache in a VM. Worked great, until I destroyed the VM: I couldn't delete the VM disks from LVM. The Proxmox kernel has bcache enabled by default and it instantly grabbed the bcache volumes. Because the disks were in use I couldn't delete them. Eventually I gave up trying to get the bcache device stopped and the disks unmounted. I just blacklisted bcache on my host in /etc/modprobe.d/ and after a reboot I could delete the orphaned disks.

bcache is easy to setup and it did give me good results but I discovered how hard it is to remove from a system. Still a good option inside a VM: The backing device can be on shared storage and the cache device can be local. No risk of data-loss if you set it to writethrough mode. Just remember to blacklist the bcache module on Proxmox first.
 
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