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Dell EMC NVDIMM-N Persistent Memory User Guide

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Battery

A battery is required to provide backup power to copy contents from DRAM to flash. Although JEDEC based NVDIMM-Ns can utilize Super Caps as backup power, DellEMC’s battery is a centralized power solution that provides a more compact, reliable, and integrated power source. Power delivery is integrated into the system board, and does not require individual cables to each NVDIMM-N that is typical of Super Cap based solutions.

On first detection of an power loss, the server activates the battery and triggers the NVDIMM-N to save its DRAM contents to flash. The Save process takes approximately a minute to complete in the T640, R640, R740/R740XD, R840, R940 and R940xa servers and 140 seconds to complete in the MX740c and MX840c servers. During this time the battery is required to provide power for backup. The battery supplies power only to server sub-systems that must be powered for the save to complete. All other subsystems are powered down or placed into a low power state to conserve battery life. After the save completes, the battery is deactivated, and the server is allowed to power down completely. In modular chassis, the batteries also provide power to the system fans to provide cooling during the NVDIMM save after an power loss event.

Table 1. Battery LED BehaviorThe following table describes the Battery LED Behavior.

Battery Operation

Green LED

Powered Off

Off

Idle (not charging and not enabled while the server is on)

Off

Maintenance Charging

On

Critical Charging (battery capacity is below minimum required for NVDIMM-N Save, server is powered on)

Blinking

Battery Enabled and Discharging (Power loss detected, Battery supplying power for NVDIMM-N Save operation)

Blinking

If a battery is not installed or not fully charged, BIOS will restore the NVDIMM-N DRAM contents from its onboard flash, but BIOS will keep the NVDIMM-N in Read-Only mode. This allows OS and applications to have access to NVDIMM-N data, and at the same time protect the NVDIMM-N from potential data loss due to power loss.

The NVDIMM-N battery is not hot swappable. To prevent data loss and potential damage to your system, ensure that the system, LEDs on the system, LEDs on NVDIMM-N, and LEDs on NVDIMM-N battery are turned off before installing or removing the NVDIMM-N Battery.

Figure 7 below shows the system board connections for the NVDIMM-N Battery cables in the R740/R740XD (Items 36 and 38). Figure 8 shows how to install and mount the battery in the R740/R740XD. Please refer to each server’s Installation and Service Manual for detailed instructions on how to install or remove the battery.

Figure 1. R740/R740XD System Board Connections
This image shows R740/R740XD System Board Connections.
NOTE:Connector locations will be different for each server. Please refer to your particular server’s Installation and Service Manual for more information.
Figure 2. R740 Battery Installation Instructions
This image shows R740 Battery Installation Instructions.
NOTE:Battery installation locations will be different for each server. Please refer to your particular Server’s Installation and Service Manual for instructions.

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