A customer has one host attached to each SP on a VNX. SP A owns LUNs 100 and 101, which
run critical applications. The customer notices that SP A has experienced a back-end failure and
consequently has lost connectivity to these LUNs. How will ALUA handle this path failure to
ensure continued connectivity to LUNs 100 and 101?
A.
The lower redirector routes I/O to the SP owning the LUNs.
B.
PowerPath immediately trespasses the LUN to the owning SP.
C.
The upper redirector routes I/O to the SP owning the LUNs.
D.
PowerPath routes traffic to the peer SP and through the CMI.
I think, the correct answer is D. Are there any other comments?
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A back-end path failure is handled much
in the same manner but is handled by the Lower Redirector. On initial path failure the
Lower Redirector routes the I/O to the SP owning the LUNs through the CMI channel. LUNs
are not trespassed initially in case the path fault is transient. Only when the system detects
a persistent path failure are LUNs trespassed to the peer SP. An additional benefit of the
lower-redirector is internal in that the replication software drivers (including meta-lun
components) are also unaware of the redirect.
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