Chapter 3: Subsystem Connection
Configuration Rules:
Following are the rules for connecting SAS interfaces across RAID
and JBOD enclosures:
1. Corresponding to SAS drives’
dual-ported
interface, two (2)
physical links are available from each disk drive, routed across
the backplane board, and then interfaced each through a 4x wide
external SAS port.
2. SAS expansion cables will be available with Infortrend’s JBODs.
Note that if many JBODs are connected, a longer SAS external
cable may be necessary to connect a JBOD from the other
direction offering path redundancy even when one of the JBODs
fails.
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.
3. 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 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).
Figure 3-5: SAS Domains
Sample Topology
3-7
