A.10.1 Direct-attach Connections
In a direct-attach connection, SAS or SATA disk drives are connected directly to a SAS card with SAS or
mini-SAS cables. One disk drive is attached to one SAS/mini-SAS connector with one SAS/mini-SAS cable
(or multiple disk drives are attached to one SAS/mini-SAS connector with one fan-out cable). The gure in
Connecting Drives Directly to the Controllerinstallation direct-attachdirect-attach connections shows an
example of direct-attach connections.
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 ConnectionsSAS expander
connectionsexpander connections.)
A.10.2 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 Controllercontrollers gurescontrollers descriptions 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.
A.10.3 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 ConnectionsSAS backplane
connectionsbackplane connections), support large congurations 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.
47
Microsemi Proprietary and Condential. Installation and User's Guide Revision 5
Introduction to SAS
To Next Page
