On Wed, Jan 28, 2004 at 04:55:34PM -0800, Patrick Mansfield wrote: > > We had the "where does the elevator go" discussion at the OLS bof. I > > think I heard agreement that the current situation of between dm and > > block is suboptimal and that we'd like a true coalescing elevator above > > dm with a vestigial one for the mid-layer to use for queueing below. I > > think this is a requirement for dm multipath to work well, but it's not > > a requirement for it actually to work. > > If the performance is bad enough, it doesn't matter if it works. It would be great to get some benchmarks to back up these arguments. eg, performance of dm mpath with a simple round robin selector, compared to a scsi layer implementation. Lifting the elevator (or lowering dm) is a big piece of work that I wont even consider unless there is very good reason; the reason probably needs to be broader than just multipath too. Even if we did decide to do this, it won't happen in 2.6. - Joe