As discussed recently on the lustre-devel mailing list:
I think the pio feature should be removed.
Quoting my email to the list:
elieve that long term it’s headed out of Lustre. It only improves performance in a limited way in certain circumstances, and harms it in various others. So it’s off by default, and, I suspect, remains completely unused. A while back I noticed its test framework test didn’t activate it correctly, and once fixed, it sometimes deadlocks (race with truncate). There’s a patch to fix that, but a problem was found in it and it has since languished.
I would still suggest you take it, Neil, as othewise you’ll complicate a bunch of potentially nasty porting working in the CLIO stack, as you apply the years of patches written with it there. Instead, I’d suggest we pull it in the open sfs branch (Sorry! It was a promising idea but it hasn’t panned out, and the current parallel readahead work isn’t going to use it.) and then eventually you could pick that up."
Patches forthcoming. I have also asked the lustre-discuss mailing list if anyone is using it, and we can change course if someone pipes up.