Ceph RBD features for Proxmox

[martijnk]

Hello all,

Sorry if this was already asked but I couldn't find it. With CEPH you can specify different features for the block device (RBD).

• Deep flatten
• Layering
• Exclusive lock
• Object map (requires exclusive-lock)
• Journaling (requires exclusive-lock)
• Fast diff (interlocked with object-map)

Can you tell me which of these options are best to enable/disable for Proxmox?

Thanks!

 

[lifeboy]

I have found that fast-diff is very useful, which requires exclusive-lock and object-map to be enabled as well.

While the selection of features at RBD image create time is nicely documented, how to modify an existing volume is not easy to find.

I wanted to enable fast-diff on images to I can use quickly see from rbd du how much space is actually being used without recreating the image.

Here's what I learned:

# rbd feature enable <pool_name>/<image_name> exclusive-lock object-map fast-diff
# rbd object-map rebuild -p <pool_name> <image_name>
Object Map Rebuild: 100% complete...done.

I thought I'd just leave it here for future reference...