APC SGI 15000 RAID - Manual (Page 127)

Drive Enclosure Installation
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6.5 SAS DEM
The drive enclosure contains eight (8) top-loadable DEMs. The DEMs provide the SAS connectivity
between the I/O module and the HDDs located within the enclosure. Each DEM connects to a single port
of the HDD based on the location within the enclosure in which it is installed. Each of the eight DEMs
installed in the enclosure has a unique I
2
C and SAS address based on a proprietary SAS address
generation scheme.
6.6 SATA Interposer Features
The drive enclosure supports an active/active SATA MUX interposer which allows simultaneous access
to the SATA HDD from both I/O modules installed in the enclosure. The MUX is implemented as a
dongle module installed in the HDD carrier assembly. Additionally, the SATA interposer allows the
power cycling of an individual HDD via SES commands.
6.7 Drive Enclosure Device Addressing
See Appendix B, “Drive Addressing”.
6.8 Grounding Checks
The product must only be connected to a power source that has a safety electrical earth connection.
Warning If more than one product is fitted in a rack, the earth connection to the rack is even more
important, because the rack will then have a high “EARTH LEAKAGE CURRENT” (“TOUCH
CURRENT”).
The earth connection to the rack must be checked before switching on, by an electrical engineer who is
qualified to the appropriate local and National standards to perform the check.