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MD3200i with ESX 4.1 - multipath - MRU or RR

Hi all.

I have a new VMWare environment on Dell R610 with Dell 5424 iSCSI switches connecting to a Dell MD3200i.

My question is - what is the recommended configuration for the iSCSI adapter within VMWare. The default is MRU (Most Recently Used) but I prefer RR (Round Robin) on ActiveActive arrays (as is the MD3200i).

Can anyone confirm this myth as there appears to be little concrete documentation on the dell site for MD3200i existence alongside VMWare....

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RE: MD3200i with ESX 4.1 - multipath - MRU or RR

Most Recently Used was the prefered due to older array firmware (LSI not Dell) and Vmware 4.0 to 4.1 transitions. Round Robin is supported now and works perfectly. To answer your questions lets define what they both mean.

•Most Recently Used (MRU) — Selects the first working path, discovered at system boot time. If this path becomes unavailable, the ESX host switches to an alternative path and continues to use the new path while it is available. This is the default policy for Logical Unit Numbers (LUNs) presented from an Active/Passive array. ESX does not return to the previous path when if, or when, it returns; it remains on the working path until it, for any reason, fails.

•Round Robin (RR) — Uses an automatic path selection rotating through all available paths, enabling the distribution of load across the configured paths.

◦For Active/Passive storage arrays, only the paths to the active controller will used in the Round Robin policy.
◦For Active/Active storage arrays, all paths will used in the Round Robin policy.


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