SATA Aggressive Link Power Management (ALPM) - call for testing

[Colin Ian King]

Hi there,

Aggressive Link Power Management (ALPM) is a mechanism where a SATA AHCI 
controller can put the SATA link that connects to the disk into a very 
low power mode during periods of zero I/O activity and into an active 
power state when work needs to be done. Tests show that this can save 
around 0.5-1.5 Watts of power on a typical system.

ALPM is now available in several SATA controllers that use the Advanced 
Host Controller Interface (AHCI). However, there is some anecdotal 
evidence that some controllers may go into a low power state incorrectly 
and this ends up causing data loss. Ubuntu has the ability to use ALPM 
but it it disabled by default since it can cause data loss on some 
machines.

We are looking for (brave?) volunteers to test ALPM for 2 reasons:

1) help to identify typical power savings on a range of machines
2) help to identify chipsets (and machines) where ALPM works reliably 
and also where it is broken and needs fixing.

An ALPM crowd-sourcing testing Wiki page has been created that describes 
a testing methodology and has a table for test results: 
https://wiki.ubuntu.com/Kernel/PowerManagementALPM

Please note that there is a possibility that ALPM MAY CAUSE DATA LOSS on 
some machines, so please ensure you have backed up your data or don't 
mind the risk in losing your data.

Colin