Adaptec ASR-8405 SGL — understanding SAS Backplane and Expander Connections for Storage Systems [76/117]

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

page 76.)

Backplane Connections

In a backplane connection, disk drives and SAS cards are attached to and communicate with each other

through 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. See

About 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.

The number of end devices is limited to the number of slots available on the backplane.

Some backplanes support daisy-chain expansion to other backplanes, allowing you to connect multiple

enclosures to a single SAS card in a host system.

SAS Expander Connections

A 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 page

76), support large congurations 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 different

role in a storage system. (For more information about how SAS expanders work, refer to the STA Web

site at www.scsita.org.)

You can connect up to 128 SAS ports to an edge expander. (A single edge expander can therefore support

up 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 possibly

SATA—end devices and expander devices). A single SAS domain can therefore comprise up to 16,384

SAS ports (and therefore up to 16,384 SAS addresses including the fanout expander).

The next gure illustrates (in very basic terms) a SAS domain and shows how SAS cards, SAS and SATA

disk drives, and expander devices can t together in a large data storage topology.

76Proprietary and Condential to PMC-Sierra, Inc.

Document No.: CDP-00283-04-A Rev. A, Issue

Serial Attached SCSI RAID Controllers Installation and User's Guide