2012-09-13 12:50 AM
Filer distributes active paths to disk across two available paths. For Fibre Channel this happens per disk; for SAS this happens per shelf (at least, that is what I have observed).
There is no absolute answer to any performance question. MP-HA distributes IO across more HBAs; OTOH now you have two controllers competing for the same FC loop. This is less relevant for SAS. But I am sure that you will be disk and/or CPU bound long before you will be HBA bound.
2012-09-13 04:42 AM
Even with 4gb fc we didn't see back end bottlenecks with 2x4gb paths to esh4... Now with with 3 and 6gb sas. 4 lanes of 3 or 6gb for 12gb or 24gb per path. Then multipath and have 24gb or 48gb to the stack. I haven't seen a case where the back end is a bottleneck.