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offering high redundancy.
•
One expansion link connects JBODs from RAID to the nearest JBOD, and
then to the farthest JBOD. Another expansion link connects to the farthest
JBOD from the opposite direction and then to the nearest JBOD.
•
Each expander controller on the SAS JBOD controls a “
SAS Domain
” that
connects one of the alternative interfaces on all of the disk drives in the
enclosure. For example, one expander unit controls Domain A, and the other
controls Domain B. In a fault-tolerant topology, the SAS external links always
connect to the SAS ports on the same SAS Domain.
•
The SAS Domains can be identified by the expanders’ locations, i.e., upper
controller slot (Controller A/Slot A) or the lower controller slot (Controller
B/Slot B).
•
On the RAID system, each RAID controller can be 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 JBOD.
