Ceph » ceph-volume

How about returning a list of the physical devices as an array in the json output? We already have the VG, so it should just be a matter of listing all PVs that are part of that VG.

This is how it is tricky :)

If a VG has 2 devices, say, /dev/sda1 and /dev/sdc1, a logical volume can be created just from /dev/sda1 and omit /dev/sdc1.

The correct thing to do is to ask LVM to provide the list of associated devices with the actual LV. This is not impossible to do, it is just a bit complicated.

Ah, yes. I hadn't considered the case of an LV with extents that only use specific PVs rather than the entire VG.

The necessary data seems to all be in there in the "lvm fullreport --reportformat json" output. There are arrays called "pvseg" which map LVs to PVs.

- get all the pvseg array entries that have an lv_uuid matching the ceph volume in question
- from these pvseg entries, get all the unique pv_uuid values
- for each unique pv_uuid value, get the pv_name (device name) from the "pv" array

Does ceph-volume currently use the lvm json report? I'm not sure when that was introduced in LVM, so the only concern might be compatibility with older versions.

We don't use --reportformat=json because Xenial doesn't support it. But LVM is still providing everything we need with comma separated values.

I am sure we can find the info, it is just going to take a bit longer to implement since it isn't straightforward

merged commit 189192b into ceph:master