LinuxQuestions.org - Possibly wrong comments in 'harddrive' pm-utils script

Hi,

I'll try to better explain what I've noticed (sorry, didn't have the time when I posted this).
Code:
#!/bin/sh



[ -x /sbin/hdparm ] || exit $NA



# Default values on AC

DRIVE_SPINDOWN_VALUE_AC="${DRIVE_SPINDOWN_VALUE_AC:-0}"

DRIVE_WRITE_CACHE_AC="${DRIVE_WRITE_CACHE_AC:-1}" 

DRIVE_POWER_MGMT_AC="${DRIVE_POWER_MGMT_AC:-254}"

DRIVE_ACOUSTIC_MGMT_AC="${DRIVE_ACOUSTIC_MGMT_AC:-0}"



# Default values on battery

DRIVE_SPINDOWN_VALUE_BAT="${DRIVE_SPINDOWN_VALUE_BAT:-6}"

DRIVE_WRITE_CACHE_BAT="${DRIVE_WRITE_CACHE_BAT:-0}" 

DRIVE_POWER_MGMT_BAT="${DRIVE_POWER_MGMT_BAT:-128}"

DRIVE_ACOUSTIC_MGMT_BAT="${DRIVE_ACOUSTIC_MGMT_BAT:-254}"



# Default devices to operate on

DRIVE_LIST="/dev/[hs]d[a-z]"



help() {

cat <<EOF

--------

$0: Control hard drive spindown, write caching, 

    power management and acoustic management.



This hook has 8 tuneable parameters:

DRIVE_SPINDOWN_VALUE_AC = time until a drive will spin down on AC

Defaults to 0, which disables drive spindown.

DRIVE_SPINDOWN_VALUE_BAT = time until a drive will spin down on battery

Defaults to 6, which will spin the drive down after 30 seconds of inactivity.



See the -S option on the hdparm manpage for more information.



DRIVE_WRITE_CACHE_AC = Whether the drive caches writes on AC

Defaults to 1, which means that the drive will cache writes internally.

DRIVE_WRITE_CACHE_BAT = Whether the drive caches writes on battery.

Defaults to 0 which means that the drive will not cache writes internally.



See the -W option on the hdparm man page for more information.



DRIVE_POWER_MGMT_AC = Drive Advanced Power Management value on AC

Defaults to 254 for max performance.

DRIVE_POWER_MGMT_BAT = Drive Advanced Power Management value on battery

Defaults to 1 for max power savings. # defaults to 128



See the -B option on the hdparm man page



Drive acoustic management:

DRIVE_ACOUSTIC_MGMT_AC = Drive Acoustic Management value on AC

Defaults to 254 for max head speed. # defaults to 0 -> AAM off

DRIVE_ACOUSTIC_MGMT_BAT = Drive Acoustic Management value on battery

Defaults to 128 for max quietness. # defaults to 254 -> actually max loudness, according to manpages



See the -M option on the hdparm man page. 



Drives to manage:

DRIVE_LIST = the list of hard drives to manage.

Defaults to "/dev/[hs]d[a-z]", which will manage up to the first 25 drives.



EOF

}



harddrive_ac () {

    for dev in $DRIVE_LIST; do

        # disable write caching, do not spin down the drive, disable APM    < caching is enabled

        # and acoustic management, and sync everything to drive.            < there's no syncing

        printf "Disabling hard drive power management for %s..." "$dev"

        hdparm -W $DRIVE_WRITE_CACHE_AC \

            -S $DRIVE_SPINDOWN_VALUE_AC \

            -B $DRIVE_POWER_MGMT_AC \

            -M $DRIVE_ACOUSTIC_MGMT_AC $dev >/dev/null 2>&1 \

            && echo Done. || echo Failed.

    done

}



harddrive_battery() {

    for dev in $DRIVE_LIST; do

        # disable write caching, enable acoustic management    < syncing goes here; missing descriptions

        printf "Enabling power management for %s..." "$dev"

        hdparm -W $DRIVE_WRITE_CACHE_BAT \

            -S $DRIVE_SPINDOWN_VALUE_BAT \

            -B $DRIVE_POWER_MGMT_BAT \

            -M $DRIVE_ACOUSTIC_MGMT_BAT -F $dev >/dev/null 2>&1 \

            && echo Done. || echo Failed.

    done

}



case $1 in

    true) harddrive_battery ;;

    false) harddrive_ac ;;

    help) help;;

    *) exit $NA ;;

esac



exit 0
Maybe this script should be checked :\
Please correct me if my understanding is somehow wrong.

bye!