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Multipathing/load-balancing across multiple HBA's in Tru64 5.1x

David Hartman_2
Occasional Contributor

Multipathing/load-balancing across multiple HBA's in Tru64 5.1x

Is there a way to control multi-pathing & load-balancing among multiple HBA's from within the 5.1x OS? My understanding is that Tru64 will dynamically load balance I/O across multiple paths, but this can cause problems with active/passive arrays. I would like to use the availability feautres akin to PVLINKS without sending I/O down multiple paths (load-balancing) to avoid 'ping-ponging' LUNS between controllers.

Thanks.
5 REPLIES
Ivan Ferreira
Honored Contributor

Re: Multipathing/load-balancing across multiple HBA's in Tru64 5.1x

Try64 has the multipath support in the kernel, and is a "failover" mode. You cannot activate both controllers, and you cannot control which will be the active controler.

But i don't know why this will be a problem with active/passive arrays, there has been active/passive arrays since the HSZ50. The operating system always tries to use the best available path.
Por que hacerlo dificil si es posible hacerlo facil? - Why do it the hard way, when you can do it the easy way?
Devesh Pant_1
Esteemed Contributor

Re: Multipathing/load-balancing across multiple HBA's in Tru64 5.1x

David,

Tru64 5.1x has a pretty good multipathing and load balancing and you should not have any ping-ponging. It will actually provide you a better bandwith and passivity is not to be seen here at all.

thanks
DP
Mulgund
Frequent Advisor

Re: Multipathing/load-balancing across multiple HBA's in Tru64 5.1x

Not sure if David want to ask this, But was just curious.
LUN's created using HSG80 controller can have preferred access path set. This LUN detail I guess will not be visible to the OS. Will this not defeat the idea of load balancing?
Larry Vatkin
Advisor

Re: Multipathing/load-balancing across multiple HBA's in Tru64 5.1x

I understand, that David's question focuses not on advantages of MP&DLB, but how to limit it's impact on active/passive arrays, that don't use HSx80 controllers. I've seen similar problems in which those controllers recognized switching of a path as a path failure, which forced them going into diagnostic mode, subsequently slowing down I/O rate.
So, in the absense of a suitable answer, I join David in his question.
Uwe Zessin
Honored Contributor

Re: Multipathing/load-balancing across multiple HBA's in Tru64 5.1x

T64 V5 knows how to tell the difference between an active and a standby path ;-)

You can still cause a failover to a standby path (well, all standby paths on a particular controller) by sendig a 'START UNIT' command down one path with SCU.
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