Many of today's S390 disk subsystems have the capability of defining 3390-1 or smaller volumes. Since you can define directories on specific devices, users have options today. If access to a specific file or set of files is being bottlenecked by device contention, the files can be put in a separate directory and that directory can be put on a dedicated device. If you use small volumes, some of the benefits you would see from PAV are available today.
PAV has many advantages, but it is not nirvana for every bottleneck problem. Basically you define alias addresses that can have exclusive access to a domain of tracks on a device. The domains cannot overlap for writes. An OS that supports PAV can move the domains around to match I/O demand. Since files in most Linux file systems potentially end up being non-contiguous, as well as the superblock issues, I doubt a file level granularity would be possible in S390 Linux. I assume the PAV support would be in the DASD device driver. I am guessing that the easiest implementation of PAV for S390 Linux would be at a partition level. Thus, each of your partitions on a DASD device could be covered by a unique alias. Is this what is being proposed? Scott Ledbetter StorageTek
