IBM 8408-44E Site And Hardware Planning page 184

Figure 98. Mode 1 connection of two ESLL or ESLS storage enclosures by using YO12 cables to one pair of SAS
adapters
5. Two independent SAS adapters to one ESLL or ESLS storage enclosure through a mode 2 connection.
v Connection by using two SAS YO12 cables to connect to the ESLL or ESLS storage enclosure.
v Supported only on AIX and Linux systems.
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Site and hardware planning