IBM 8408-44E Site And Hardware Planning page 167

Figure 81. Mode 2 connection of a 5887 enclosure by using X cables to two pairs of SAS adapters
7. Four single FC 5901 or FC 5278 adapters to one 5887 enclosure via a mode 4 connection.
v 5887 enclosure with four sets of six hard disk drives (HDDs).
v Connection using dual SAS X cables to connect to the 5887 enclosure.
v Supported only on AIX and Linux systems.
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