Two storage arrays are physically attached but only one of them was appearing in the system status reports. This is a very rare occurrence but should be highlighted. Consider other solutions first.
R640xl with two ME4084/U840 storage arrays attached. This could be a problem anywhere two storage arrays or more are attached.
The second CPU was not responsive at power on during the POST tests.
All tests showed that half of the logical disks and all fiber connections were online. The storage array logs and management menus indicated that all was working as expected and healthy. There were no reports of failure in the Dell TroubleShooting/SupporAssist logs or iDRAC as the part never failed.
The power switch was pushed on the system which caused a power cycle, not just a warm boot. The hardware forces a Power On Self Test (POST) as part of the initialization process. The second CPU did not respond and anything attached to it did not come online. This includes half of the memory and half of the PCIe slots with the installed PCIe cards.
This can be detected in the system by running free -m and determining how much memory is configured. The r640xl systems sold by Broadcom should have 384GB of RAM installed but a crippled system will only have 192GB of RAM displayed. Also, comparing the output of multipath -ll with the historical multipath files in /home/csr/history will show that only have the logical volumes are appearing. These are two quick ways to determine that this scenario applies.
The iDRAC menus will only show one CPU and 192GB of RAM. There will be no errors because the components did not fail. They were missing during a power up.
The system was powered off, and this can be done using the iDRAC remotely, and after three minutes it was powered on again. The iDRAC will now report two CPUs and 384GB of memory. The system will typically come online without need for further intervention.