Up until now the default io scheduler was set in kernel arguments.
This is dangerous, intrusive, unportable and indeterministic.
bug#754334 added tuned dependency which should have done exactly this, but as it turns out (bug#878511) it does not applies the policy dynamically.
So we need some solution within vdsm or bootstrap. A solution for vdsm is available at.
But as tuned entered the picture it may be wiser to perform this at bootstrap level, dropping it when tuned is ready.
*** This bug has been marked as a duplicate of bug 870159 ***