On Thu, Mar 21, 2019 at 11:27:42AM +0100, Lukas Czerner wrote: > > Snapshot of a thinspanshot is allowed though, so we might want to > include those. Not sure if it's wise to do it by default, but regardless > it's probably something for a separate change. Yeah, it's definitely a separate change. One potential design question is that for a thin volume, you can do both a thin or a think snapshot, and in some cases one might succeed while the other will fail. So do we make this choice be a parameter that we set in the config file, or do we try to see if there is sufficient spare freespace for a thick snapshot (and then do that), or a thin snapshot (and then do that) --- and which should use prefer? The other thing I'll note is that in order for us to tell whether something is a thin or thick LV, we're going to to need to ask lvs to return multiple parameters, so the optimization of using: for NAME in $(lvs -o lv_path --noheadings -S...) ; do ... done will no longer work. (Or we end up calling lvs a second time, which is less efficient.) Just curious --- do we know how commonly thin LV's are being used by customers of various distros? I assume enterprise distro users will be the most conservative, but how common is the uptake of thin LV's by Fedora and OpenSuSE users? - Ted
