IBM 8408-44E Site And Hardware Planning page 186

Figure 100. Mode 2 connection of ESLL or ESLS storage enclosure by using YO12 cables to a single SAS adapter
7. Two pairs of SAS adapters to one ESLL or ESLS storage enclosure through a mode 2 connection.
v For SAS adapter pairs, you must attach the cables to the same port on both adapters.
v Connection by using SAS X12 cables to connect to the ESLL or ESLS storage enclosure.
v Supported only on AIX and Linux systems.
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