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тАО05-01-2009 05:05 AM
тАО05-01-2009 05:05 AM
I'm still learning my way through HP UX and I got a questions for you guys. We're setting up our environment right now with an rx6600 Itanium with 11.31 and EVA 6100. All my luns are showing 8 paths, 4 active and 4 standby. All active paths are getting on the same controller but using different fabric.
Why there's 4 paths on standby. Is there a way to use all 8 of them (if it's recommended)? If not, can I change the active path used to balance it on both controller?
I must specify that no preferred path is configured on the EVA or on the lun. You'll find attached to this post the result of scsimgr get_info all_lpt -D /dev/rdisk/disk118 (one of the SAN lun)
Thank you to everyone...
Solved! Go to Solution.
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тАО05-01-2009 05:21 AM
тАО05-01-2009 05:21 AM
Re: EVA lun path question
You should use all 8 paths for each device. In most cases though if a failure occurs multiple paths will disappear at the same time.
> All active paths are getting on the same controller but using different fabric.
Not sure what you are saying here but you should ensure that i/o is balanced on both (all) server HBAs by splitting the active paths to both (all) server HBAs. Or use the new disk management that is available with HP-UX 11.31
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тАО05-01-2009 05:23 AM
тАО05-01-2009 05:23 AM
Re: EVA lun path question
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тАО05-01-2009 05:33 AM
тАО05-01-2009 05:33 AM
Re: EVA lun path question
On the SAN, each controller got 2 ports, one on fabric A and one on B. If I compute correctly, that makes 8 paths.
The load_bal_policy is least_cmd_load. When transfering data on the SAN, all 4 ports are used but all getting on controller A. I want to balance the load on the 2 controller.
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тАО05-01-2009 06:52 AM
тАО05-01-2009 06:52 AM
Re: EVA lun path question
> all 4 ports are used but all getting on controller A
Is that controller A of the EVA? Unless you have a low end EVA, check the LUN presentation and controller ownership on the EVA.
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тАО05-01-2009 07:03 AM
тАО05-01-2009 07:03 AM
Re: EVA lun path question
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тАО05-01-2009 08:32 AM
тАО05-01-2009 08:32 AM
SolutionThe way the EVA works, all read operations are proxied from the owning to non-owning controllers anyway, (that's why its called *asymmetric logical unit access or ALUA) so you actually gain very little by being able to use the other controller for a LUN - you gain slightly on writes, but not that much (writes have to be mirrored into the cache on both controllers anyway unless you specifically turn that feature off). IIRC the EVA DCM MPIO module for windows are actually able to send writes to the non-owning controller, but all reads are still sent to the owning controller - as this DCM was out before the 11iv3 stack was released, I can only assume that the IO folks on the HPUX team looked at the gain you get from sending writes to non-owning controllers and decided the minor gain in performance wasn't worth the trouble of coding in similar features.
So if you are *really* concerned about missing out on a bit of performance, then make sure that you use a volume manager to aggregate your IO across 2 LUNs which are owned by different contollers - this is nearly as true for windows as it is for HPUX.
HTH
Duncan
I am an HPE Employee
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тАО05-01-2009 08:40 AM
тАО05-01-2009 08:40 AM
Re: EVA lun path question
That's the kind of information I was looking for. It does make sense.
Thank you all for your commitment. This is surely a nice forum....