On Mon, 02 Jun 2014 11:51:52 +0200 Sebastian Parschauer <sebastian.riemer@xxxxxxxxxxxxxxxx> wrote: > > Having a scheduler for RAID0 doesn't make any sense to me. > > RAID0 simply passes each request down to the appropriate underlying device. > > That device then does its own scheduling. > > > > Adding a scheduler may well make sense for RAID1 (the current "scheduler" > > only does some read balancing and is rather simplistic) and for RAID4/5/6/10. > > > > But not for RAID0 .... was that a typo? > > Nope, we have our RAID-1+0. So it is more or less a RAID-10 and putting > the scheduler to this RAID-0 layer makes sense for us. I still cannot imagine how this would work. RAID-0 has no decisions to make, so no where for a scheduler to fit. Just to clarify: is this md/raid0 over md/raid1 or md/raid0 over hardware/raid1? > > Could you do a graph? I like graphs :-) > > I can certainly seem something has changed here... > > Sure, please find the graphs attached. I've converted it into percentage > so that number of bios can be compared to number of requests. Thanks. > > > > Show me the code and I might be able to provide a more detailed opinion. > > I would say let the user decide whether an MD device should be equipped > with a scheduler or not. We can port our code to latest kernel + latest > mdadm and send you a patch set for testing. Just give me some time to do it. In the first instance, I just want to get a concrete idea of what you have done because what you have said doesn't make sense to me. I'm happy to look at code against a not-quite-current kernel to get that idea. But I'm also happy for it to be against the latest, whatever suits you. NeilBrown
Attachment:
signature.asc
Description: PGP signature
