Short bullet points as I may get round to expanding this:
ASRock C2750D4I with 1.35V DRAM modules.
VMware client showed health status as an alert due to low RAM voltage (expected as they are 1.35V but it seems the machine’s BIOS sets the threshold for 1.5V RAM modules)
ESXi 6.0 health indicated VCCM1 (voltage controller for memory 1??) was in a warning state at 1.35V.
I found a statically linked copy of ipmitool at https://fattylewis.com/ipmitool-on-esxi-6/ which I uploaded to the ESXi host in question. This worked first time!
./ipmitool chassis status System Power : on Power Overload : false Power Interlock : inactive Main Power Fault : false Power Control Fault : false Power Restore Policy : previous Last Power Event : ac-failed Chassis Intrusion : inactive Front-Panel Lockout : inactive Drive Fault : false Cooling/Fan Fault : false
I checked the sensors:
./ipmitool sensor list ....<snipped>... ATX+5VSB | 5.040 | Volts | ok | 4.050 | 4.260 | 4.500 | 5.490 | 5.760 | 6.030 +3VSB | 3.440 | Volts | ok | 2.660 | 2.800 | 2.960 | 3.620 | 3.800 | 3.980 Vcore1 | 1.050 | Volts | ok | 0.540 | 0.570 | 0.600 | 1.490 | 1.560 | 1.640 Vcore2 | na | Volts | na | 0.540 | 0.570 | 0.600 | 1.490 | 1.560 | 1.640 VCCM1 | 1.350 | Volts | nc | 1.210 | 1.280 | 1.380 | 1.650 | 1.730 | 1.810 VCCM2 | na | Volts | na | 1.210 | 1.280 | 1.380 | 1.650 | 1.730 | 1.810 ....<snipped>...
There we have it, the warning is set for 1.38V. This can be changed with IPMI tool:
./ipmitool sensor thresh VCCM1 lnc 1.32
Now we check the result:
./ipmitool sensor list VCCM1|grep VCCM
VCCM1 | 1.340 | Volts | ok | 1.210 | 1.280 | 1.320 | 1.650 | 1.730 | 1.810
VCCM2 | na | Volts | na | 1.210 | 1.280 | 1.380 | 1.650 | 1.730 | 1.810
And the VMware health status got fixed too!
For now, I will need to run this command after every reboot or reset of the IPMI management controller. I guess I should automate this for system boot-up….
FOLLOW-UP: I have just upgraded the BMC firmware from v0.27.00 to v0.30.00 and the issue seems to be resolved as the VCCM threasholds have been redefined:
./ipmitool sensor|grep VCCM VCCM | 1.350 | Volts | ok | 1.090 | 1.120 | na | na | 1.720 | 1.750
Oh well, this was an interesting learning experience. Maybe this ipmitool info will help someone else. Note that this is a useful tool as it allows one to configure the management controller from the host while ESXi is running. Useful perhaps to configure the LAN, change the admin user or reset the controller entirely. For example, we can configure the IP address as follows:
./ipmitool lan set 1 ipsrc static ./ipmitool lan set 1 ipaddr 172.16.1.5 ./ipmitool lan set 1 netmask 255.255.255.0 ./ipmitool lan set 1 defgw ipaddr 172.16.1.1 ./ipmitool lan set 1 arp respond on ./ipmitool lan set 1 arp generate on ./ipmitool lan set 1 arp interval 60
Extra info about using ipmitool and controlling the fans on this motherboard at https://blog.chaospixel.com/linux/2016/09/Fan-control-on-Asrock-C2750D4I-C2550D4I-board.html