On Wed, May 22, 2013 at 05:14:18PM -0400, Mikulas Patocka wrote: > This is updated dm-switch. It has better documentation and better error > reporting in message function. ... > --- > > From: Jim Ramsay <jim_ramsay@xxxxxxxx> > > dm-switch is a new target that maps IO to underlying block devices > efficiently when there are a large number of fixed-sized address regions > but there is no simple pattern to allow for a compact mapping > representation such as dm-stripe. Interesting. I have been working on something similar recently, for not dissimilar reasons. However the approach I had been taking was to extend __choose_pgpath to take a pos parameter indicating the block being requested, and then add a new dm-pref-hint multipath driver, which effectively does a round-robin but prefers any path that has the "pref" bit. Currently the dm-pref-hint driver is extremely hacky and reaches down into the scsi_device to do an appropriate CDB along each path to get the pref-map, or I'd post it for comments. I'm interested in why the decision was made to have dm-switch as a separate device-mapper layer? Are there a corresponding set of patches to multipath-tools which know how to do the setup of each individual path? J. -- Is this real - that's the first thing I think every morning. This .sig brought to you by the letter N and the number 24 Product of the Republic of HuggieTag -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
