On 02.06.2014 12:20, NeilBrown wrote: > On Mon, 02 Jun 2014 11:51:52 +0200 Sebastian Parschauer > <sebastian.riemer@xxxxxxxxxxxxxxxx> wrote: >> >> 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? We have both variants but tested the scheduler with servers without HW RAID and only 4 HDDs. On the production servers there are 24 HDDs, every 2 HDDs are in md/raid1 or HW RAID-1 and these 12 RAID-1 devices form an md/raid0 device. This is the only PV for LVM and LVs are the customer volumes exported via SCST/SRP. These are used by virtual machines on other servers. So the scheduler has to bring some fairness to the customer volumes so that a streaming customer can't block a database customer completely with his big sequential IOs as these would have priority. But our goal with a scheduler is to reduce latency for everyone. I hope this is clear, now. Just tell me if not. ;-) -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
