On Friday, August 27, 2021 at 12:42:54 PM Christoph Hellwig wrote: > > > >On Fri, Aug 27, 2021 at 02:28:58PM +0000, Tim Walker wrote: >> There is nothing in the spec that requires the ranges to be contiguous >> or non-overlapping. > >Yikes, that is a pretty stupid standard. Almost as bad as allowing >non-uniform sized non-power of two sized zones :) > >> It's easy to imagine a HDD architecture that allows multiple heads to access the same sectors on the disk. It's also easy to imagine a workload scenario where parallel access to the same disk could be useful. (Think of a typical storage design that sequentially writes new user data gradually filling the disk, while simultaneously supporting random user reads over the written data.) > >But for those drivers you do not actually need this scheme at all. >Storage devices that support higher concurrency are bog standard with >SSDs and if you want to go back storage arrays. The only interesting >case is when these ranges are separate so that the access can be carved >up based on the boundary. Now I don't want to give people ideas with >overlapping but not identical, which would be just horrible. > Christoph - you are right. The main purpose, AFAIC, is to expose the parallel access capabilities within a LUN/SATA target due to multiple actuators. I hope the ranges are *always* contiguous and *never* overlapping. But there's no telling what somebody has up their sleeve. Best regards, -Tim
