>I thought I understood how PAV works and it was my impression that the i/o >subsystem knew the addresses belonged to a PAV and would/could drive >simultaneous i/o to the phys device. If so ... then the dasd driver would >register a single disk with the block layer.
The DASD driver registers one disk for the base and one disk for each alias. > Which means that lvm1 would >not know about the multiple PAV addresses used by the i/o subsys ... only >seeing a single disk. No, see above, it sees multiple addresses and recognizes that they all belong to the same physical disk. >However, coming in through scsi, with multiple >interfaces out to the storage, you would indeed see multiple disks >registered with the block layer ... all of them mapped to the same phys >disk. This is a situation in which I think you'd use lvm1 with its support >for multi-paths. PAV exists only for ESCON or FICON, not SCSI. >MD has also introduced multi-path support by adding an mp >personality. Its job is to aggregate the multi-path disks and present them >as a single md volume. We prefer LVM for various reasons. For more details, see my WAVV-presentation (www.linuxvm.org). Klaus Bergmann
