Silicon Graphics InfiniteStorage 6120, User Manual

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The InfiniteStorage 6120 System Hardware
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1.2.5 Drive Expander Module (DEM) Card
The InfiniteStorage 6120 contains eight (8) top-loadable, hot-swappable DEMs
(Figure 9)
. The
DEMs provide the SAS connectivity between the controllers and the HDDs located with the
enclosure.
The DEMs are organized into four module pairs, with each module pair controlling a bank of 15
drives. If a DEM card fails, its sister card will provide continuous operation of the unit until a
replacement is inserted bringing the unit back to full redundancy.
Each DEM
(Figure 10)
connects to a single port of the HDD based on the location within the enclosure
within which it is installed. Each card provides power control signals to each drive slot. It controls
HDD identify/service LEDs and monitors the status from partner DEM. Each pair of DEMs supports
15 drives.
Figure 9. DEM Card Locations (Viewing from Top)
DEM Card x 8
Figure 10. DEM Card
Locking Mechanism