Chapter 1: Implementation Overview 11Understanding storage provided by native disk shelvesConnections andloopsDisks are inserted in disk shelves connected to the gateway or N series storagecontroller. The connection from a storage controller to the disk shelves, whichmight be daisy-chained, is sometimes called a loop. The loops are described asfollows:◆ The A loop or A channel is the connection from the storage controller to theA port on the disk shelf module (not the A port on the storage controller orhost bus adapter).◆ The B loop or B channel is the connection from the storage controller to theB port on the disk shelf module (not the B port on the storage controller orhost bus adapter).On a stand-alone system, you can use one or two connections between thestorage controller and the disk shelf. Using two connections providesredundancy. A connection can be from any free FC initiator port on the storagecontroller; if you are using just one connection, that connection can be to eitherdisk shelf module.In an HA pair, you have the option to provide redundant connections through theData ONTAP Multipath Storage feature. (See Appendix B, “Setting up andManaging Multipath Storage,” on page 65 for more details.)The following illustration shows a stand-alone system with two redundantconnections to the disk shelf, one to each disk module.ABOut InIn OutGatewaystorage controllerConnections tothird-party storage arraysDisk shelf 1B loopA loop0a 0b 0c 0d
