The number of direct-attached disk drives is limited to the number of phys supported by the SAS card.(Note that there may be multiple phys within a single connector. See SAS Expander Connections on page72.)Backplane ConnectionsIn a backplane connection, disk drives and SAS cards are attached to and communicate with each otherthrough a system backplane.There are two types of backplane connections, passive and active. When connecting to either backplane,it’s important to properly connect your disk drive LEDs in order to identify disk drive conditions. SeeAbout Your RAID Controller on page 17 for your RAID controller Activity LED connections and locations.Once you have connected to a backplane, use maxView Storage Manager to manage your disk drives.For more information, refer to the maxView Storage Manager User’s Guide on the Adaptec InstallationDVD.The number of end devices is limited to the number of slots available on the backplane. For example,the Adaptec S50 enclosure, which contains an expander, is a backplane connection that supports up to12 SAS or SATA disk drives.Some backplanes support daisy-chain expansion to other backplanes. For example, you can daisy-chain(connect one to the next) up to nine Adaptec S50 enclosures to a single SAS card in a host system.SAS Expander ConnectionsA SAS expander device literally expands the number of end devices that you can connect together.Expander devices, typically embedded into a system backplane (see Backplane Connections on page72), support large configurations of SAS end devices, including SAS cards and SAS and SATA disk drives.With expander devices, you can build large and complex storage topologies.There are two types of SAS expanders: fanout expanders and edge expanders. Each performs a differentrole in a storage system. (For more information about how SAS expanders work, refer to the STA Website at www.scsita.org.)You can connect up to 128 SAS ports to an edge expander. (A single edge expander can therefore supportup to 128 SAS addresses.)You can connect up to 128 edge expanders to a fanout expander.You can use only one fanout expander in any single SAS domain (a topology of SAS—and possiblySATA—end devices and expander devices). A single SAS domain can therefore comprise up to 16,384SAS ports (and therefore up to 16,384 SAS addresses including the fanout expander).The next figure illustrates (in very basic terms) a SAS domain and shows how SAS cards, SAS and SATAdisk drives, and expander devices can fit together in a large data storage topology.72Proprietary and Confidential to PMC-Sierra, Inc.Document No.: CDP-00277-02-A Rev. A, Issue:Serial Attached SCSI RAID Controllers Installation and User's Guide
