> It is true that the controllers in the 2540 act as active-standby on a > per-drive level, with each controller being responsible for six drives > unless a controller or drive interface fails. This means that it (ideally) > makes sense for the 2540 to communicate with MPxIO so that data is normally > sent to the controller which is active for that drive. However, it is quite > odd to export a LUN-per-drive so these smarts may not exist. > > As I mentioned before, it used to be that the load was perfectly distributed > across the two FC links and the two controllers, resulting in excellent > performance. Now MPxIO makes different decisions so the load is not > balanced any more. It may be that I could write a script to encourage MPxIO > to re-adjust the paths after boot so that they are (temporarily) optimum for > my arrangement. I am not sure how MPxIO works but it is quite possible that > its final decisions are based on ordering/timing of other events which might > change with a new kernel or device drivers. > > Note that this scenario only really applies to the case where each drive is > exported as a LUN (as I am doing). With a multi-drive LUN this optimization > goes away. > > With the current situation, I see perfect vlun load distribution via 'zpool > iostat -v' but not to the device level as shown by 'iostat -x'.
Bob, Hmm, that's an interesting config...kinda an expensive but fast JBOD then? I'm pretty sure MPxIO is not responsible for deciding which path is active and which is passive. My understanding is that it's up to the 2540 config. Is CAM reporting that all volumes are on their preferred paths? I assume you have been looking at iostat with the -Y flag? You should only see io moving down the active controller port so I would expect that it you have 12 volumes with 6 assigned to one port and 6 assigned to another and they are on their preferred path, you should see an equal load on on both. You would see even better throughput if you have 4 connections to the array (the dual paths to the individual controllers would be load balanced (symmetric)...though I'm not sure how much that would give you with your config (one drive/volume). --Brett _______________________________________________ storage-discuss mailing list [email protected] http://mail.opensolaris.org/mailman/listinfo/storage-discuss
