• Mac OS X Server,  Network Infrastructure,  Xsan

    Fibre Channel Switches vs. Hubs

    In the FC-AL (Fibre Channel Arbitrated Loop) protocol, when devices enter loops, they send out a Loop Initialization Primitive (LIP) request for an address. All other activity on the loop then comes to a halt as each node reestablishes its connection. Since a hub-based fabric is one large arbitrated loop (which can in many cases similarly be built without the actual hub but with less aggregated speed), it must be entirely rebuilt every time any device is rebooted, added to the loop or removed from it. This causes the potential for processing errors, iNode issues/volume errors and even physical disk failures. A “LIP storm” can also cause multiple devices to…