SP failover direct attached Hosts

Question

Hi guys

I'm new in the emc community. I have a question about the vnx sp failover (LUN trespass).

If I have a host with two HBA connected. (one to each SP)

I'm right if I say that when a host HBA, a cable or a SP HBA fails the host lose the connection to all the LUN that are owned by the SP that something of the above things failed ?

My interpretation was always that only if an SP completly fails the LUN will be trespassed to the other SP.

Hopefully someone can clearify this for me.

Thanks in advanced !

Cheers

Mark

dynamox · Accepted Answer

if host is connected to  SPA and SPB, that LUN will simply trespass to SPA and serviced there.  I don't remember how ALUA changes things becuase it can service I/O from the alternative SP through the internal CMI bus but i think it only happens for so many I/O before it actually trespasses the LUN.

itch1 · Answer

Hi dynamox Thanks for your answer. So a LUN owned by SPB can handle incoming host traffic from SPA right ? Cheers

dynamox · Answer

typically trespass is initiated by the host multi-pathing software. So if you are using PowerPath or MPIO, losing a path (HBA/Cable/SFP) the host will trigger the failover to the alternate SP.

brettesinclair · Answer

For ALUA/Failover mode 4, ownership of the trespassed lun is transferred back to the optimal SP if the non-optimal SP processes over 64,000 I/Os

dynamox · Answer

Thank you Brett, pretty large number of I/O ..they probably wanted to prevent trespass storms.

kelleg · Answer

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glen

VNX

SP failover direct attached Hosts

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