I/O module bays 3 and 4 are connected to each blade server bay and both disk storage module bays in the BladeCenter S chassis.
The two bays also support Ethernet switch modules, Fibre channel switch modules or pass-thru modules (optical and copper) if the disk storage modules are not being used.
If you are implementing a single SAS connectivity module, install it in I/O module bay 3.
See Planning for SAS connectivity module zoning for more information about configuring the integrated shared storage when using SAS connectivity modules.
If you are implementing a RAID storage solution you must install two SAS RAID controller modules, one in I/O module bay 3 and the other in I/O module bay 4. In addition, you must install the two battery backup units, which provide backup for the SAS RAID controller modules cache.
See Planning for SAS RAID controller module for more information about configuring the integrated shared storage when using SAS RAID controller modules.