In the event that a number of OSDs have failed, and you are unable to recover them via the ceph-object-store tool, your cluster will most likely be in a state where most, if not all, RBD images are inaccessible. However, there is still a chance that you may be able to recover RBD data from the disks in your Ceph cluster. There are tools that can search through the OSD data structure, find the object files relating to RBDs, and then assemble these objects back into a disk image, resembling the original RBD image.
In this section, we will focus on a tool by Lennart Bader to recover a test RBD image from our test Ceph cluster. The tool allows the recovery of RBD images from the contents of Ceph OSDs, without any requirement that the OSD is in a running or usable state. It should be noted that if the OSD has been corrupted due to an underlying file system corruption, the contents of the RBD image may still...