Ceph

h1. Reference counter for protected snapshots

h3. Summary

For application dynamically/frequently creating/updating later cloned virtual machine

template it may be useful to run periodic protected snapshots garbage collection of no

longer used templates i.e. protected snapshots whit no attached clones.

This currently implies scanning the cluster for potential clones like "list children"

does which is a potentially expensive operation. In this case, a clone reference counter

would be perfectly fine to decide whether the snap may be unprotected.

Previously protected snapshots could fallback to the "list children" behavior. Any call

to "list children" could possibly init the reference counter on these snapshots.

h3. Owners

* Jean-Tiare Le Bigot (jean-tiare.le-bigot@ovh.net)

* Name (Affiliation)

* Name

h3. Interested Parties

* Loic Dachary <loic@dachary.org>

* Name (Affiliation)

* Name

h3. Current Status

Removing protected RBD snapshots is potentially extremely expensive as we need to scan the whole cluster for linked clones

h3. Detailed Description

h3. Work items

h4. Coding tasks

# add ref counter in image header

# add compatibility layer / lazy creation for snapshots created earlier

# Task 3

h4. Build / release tasks

# Task 1

# Task 2

# Task 3

h4. Documentation tasks

# Task 1

# Task 2

# Task 3

h4. Deprecation tasks

# Task 1

# Task 2

# Task 3