Kernel 2.7 wishlist/framework for multi pathed I/O

Multi-path access to storage devices is an important feature for high availability environments as well as for storage area networks. The general idea is to spread I/O over several paths to gain reliability and speed. There are some approaches that implement this on the device driver level but the focus of this BOF will be the generic block layer implementation.

With the 2.6 kernel there are basically two block layer multi-path methods. One is the multipath RAID discipline and the other is the multi-path target for the device mapper. However both aproaches face several problems that originate from the way Linux does (or does not) handle I/O.

The goal of this BOF is to discuss these problems and restrictions, collect ideas how to get around them and think of requirements for the 2.7 kernel.