[jonhermansen]

If you are using LVM on all of your filesystems, it seems like a bad idea to use a file residing on LVM block device as another PV. And actually I'd be surprised if this was even allowed. Though maybe it is difficult to detect.

You'd effectively send all block changes through LVM twice (once through the file, then through the underlying block device(s))

[labawi]

LVM is just fancy orchestration for the device-mapper subsystem with some headers for setup information.

For block operations it's no different from manual setup of loop-mounted volumes, that also need to travel a couple of layers to hit the backing device.

Though there is an important caveat - LVM is more abstracted, making it easier to mistakenly map a drive onto itself, which may create a spectacular failure (haven't tried).