53
Number
Description
RAID controller A
RAID controller B
Expansion system controller A
Expansion system controller B
Dual-port SAS drives
Expander
To another expansion system
•
Fault-tolerant links to SAS disk drives
-
The SAS expansion cables are bundled with the expansion systems. Take note
that if there are many expansion systems connected, a longer SAS external
cable, approximately measured 120cm, may be needed to connect an expansion
system from the opposite direction for a higher redundancy.
-
One expansion link connects the expansion system from a storage system with
HBA/RAID card to the nearest expansion system, then to the most distant
expansion system. Another expansion link connects to the most distant
expansion system, from the opposite direction to the first expansion system from
the storage system.
-
Each expander controller on the SAS expansion system controls a
SAS domain
that connects to one of the alternative interfaces of the disk drives in the
enclosure
. For example. One expander unit controls Domain A while the
other expander controls Domain B. In a fault-tolerant topology, the SAS
external links always connect to the SAS ports of the same SAS domain.
-
Identify the SAS domains by the location of the expanders: the left controller is
controller A, the right is controller B.
-
On a storage system, each controller is considered as managing a separate SAS
domain. With the help of the port selector mechanism on the MUX boards, the
idea of SAS domain applies even when SATA drives are used in a dual controller
expansion system.
