I don't have a full answer to your question. But I want to avoid a misconception:
- mutipathing in z Architecture means a device can be reached by more than one path, most often this means more than one CHPID leads to the device, and each CHPID is connected to a different controlunit. - Without PAV: when a device in handling an IO, other IOs will be queued, for example by CP (reported by Pefkit). But also Linux, SFS, DB2VM, xxx know that classically a device can handle one one IO, and will queue other IOs (not reported by Perfkit). - PAV at the other hand makes it possible to have more than 1 I/O active on a single device. PAV is kind of a ly: a given device address can still have only one IO active; with PAV one assigns alternate device addresses to a single device. With PAV: when CP gets IO requests from different users for the same device, it will look for a free PAV address and may be able to launch it instead of queueing it. Linux -as far as I know- is also PAV aware, so it can launch more than one IO on condition that one gives it PAV addresses, otherwise it won't be able to exploit it. 2009/6/30 RPN01 <[email protected]> > Before I put something huge together to test this, I thought I’d pass it > by all the experts. > > Linux has the ability to multipath, and z/VM supports multipathing via PAV. > There’s lots of documentation and studies showing that you can attach / > dedicate the PAV addresses to a Linux LPAR or guest, and implement > multipathing to DASD devices. This seems to be fairly clearly researched and > understood. > > What I’m wondering about would be multiple links to the same minidisk > (partial 3390, as opposed to a full volume) backed by a PAV multi-address > environment sustained by z/VM. Would it help I/O throughput to have multiple > MW minidisks set up in Linux as multipathing, if they were on a DASD with > PAV enabled, and having several physical addresses? Are there any got’chas > to this configuration? Any reason why it wouldn’t work? > > -- > Robert P. Nix Mayo Foundation .~. > RO-OE-5-55 200 First Street SW /V\ > 507-284-0844 Rochester, MN 55905 /( )\ > ----- ^^-^^ > "In theory, theory and practice are the same, but > in practice, theory and practice are different." > > -- Kris Buelens, IBM Belgium, VM customer support
