EonStor DS S48 Series Hardware Manual
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that if many JBODs are connected, a longer SAS external cable (e.g., a
120cm or 170cm cable; refer to
JBOD Connections
) may be necessary
for connecting a JBOD from the opposite direction 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.
