ISSUE:
Upgrade to iLO4 2.4.0 (SPP 2016040), found The server was failed to boot ESX from SD Card. The same issue existed in iLO4 2.4.4
Root Cause:
iLO4 2.4.x will damage the partition table of SD Card/USB Flash，Not Clear it is damaged during the executing phase or stopping phase
Solution :
Rollback iLO4 to 2.3.0 (SPP 2015100)
Create USB Key of SPP 2015100
Boot with the USB
Downgrade the iLO4 firmware with interactive method
Reformat the SD Card/USB Flash
Retrieve the SD Card from server
Format it into empty status in PC （Linux）
Delete the partition table
Create DOS partition table
Create a DOS partition (0x0b)
Format the DOS partition
Insert the empty SD Card into Gen8
Reinstall ESX into SD Card
Format the SD Card with FAT32
Power outage of the server Lauch iOL remote console Insert CD of ESX iso image file Reboot with CD to install ESX
Lessons
Never trust a Company not in stable state
How to format Micro SD Card in MicroServer Gen8:
Download gparted live CD at
http://downloads.sourceforge.net/gparted/gparted-live-0.26.1-5-i686.iso
And Launch it from iLO client