Since most of what we’re talking about is unnecessary complexity for no real gain, what concrete metric do you think would be useful exactly? I just pointed out that you can get the same management advantages without it (say for a dev environment or rollbacks or whatever). And you get a simpler, cleaner story without extra layers if you don’t want to use lvm (such as in production), which you can’t get from O_DIRECT.

I also have this thread from Linus calling O_DIRECT brain damaged and to never use it. [https://lkml.org/lkml/2007/1/10/233]