Aggressive Link Power Management (ALPM)

Overview

Aggressive Link Power Management (ALPM) is a mechanism for reducing SSD/HDD power consumption. If ALPM is enabled, SSD goes into low-power mode when SSD has no I/O activity. On I/O request, SSD power is resumed.

Enabling ALPM in Windows

* HIPM = Host Initiated Link Power Management
* DIPM = Device Initiated Link Power Management

The Link Power Management option is hidden/disabled by default in Windows advanced power options, and it is required to add the support into Windows registry:

1. Adding the ALPM – HIPM/DIPM option to Advanced Power Settings.
   1. Download the Add_LPM.reg (Right click and Save link as...).
   2. Right click on the downloaded Add_LPM.reg file and click on Merge.
   3. After the success message appears, restart the unit.
2. Removing the ALPM – HIPM/DIPM option from Advanced Power Settings.
   1. Download the Remove_LPM.reg (Right click and Save link as...).
   2. Right click on the downloaded Remove_LPM.reg file and click on Merge.
   3. After the success message appears, restart the unit.
3. Configuring the ALPM – HIPM/DIPM option in the Advanced Power Settings.
   1. Click on the Start button.
   2. Type Power Options in the Start search box and press Enter.
   3. In the Power options window, click on the Change plan settings of the current power plan.
   4. In the Plan Settings window, click on the Change advanced power settings.
   5. In the Advanced Plan Settings click on the Hard disk option and expand it.
   6. The following settings are responsible on the ALPM:

• ALPM – HIPM/DIPM. It will set the Link Power Management policy:
  • Active: Neither HIPM or DIPM allowed
  • HIPM: HIPM only is allowed
  • HIPM+DIPM:HIPM and DIPM are allowed
  • DIPM: DIPM only is allowed
  • Lowest:HIPM, DIPM and DEVSLP are allowed (if DEVSLP is supported by the storage device).
• ALPM – Adaptive. It will set the period of AHCI link idle time before the link is put in the slumber state when you have HIPM, DIPM, HIPM+DIPM or Lowest set above. It can be set to be from 0 to 300,000 milliseconds. If the Active is set above, then this will have no effect.

Enabling ALPM in Linux

• Create text file /etc/pm/power.d/sata_alpm

#!/bin/sh
for i in /sys/class/scsi_host/host*/link_power_management_policy; do
echo min_power > $i
done

• Make it executable

$ sudo chmod +x /etc/pm/power.d/sata_alpm

• Reboot, check that SATA power management policy have been changed

$ cat /sys/class/scsi_host/host*/link_power_management_policy
min_power
min_power

• To disable ALPM simply delete file /etc/pm/power.d/sata_alpm

sudo rm /etc/pm/power.d/sata_alpm