[dm-devel] Questions regarding request based dm-multipath and blk-layer/elevator

[Peter Grandi]

> 1. With request based multipath, we have 2 elevators in the
>    path to the device. Doesn't 2 idling I/O schedulers affect
>    performance? Is it better to use the noop elevator for the
>    dm device? [ ... ]

Usually "metadrivers" (DM, MD, 'loop', ...) in Linux use only
one elevator (and it should be that of the _physical device_).

But if you are concerned by that kind of stuff, consider also
the impact of the (short-sightedly idiotic, and IIRC it cannot
be disabled) plugging/unplugging logic.