Novell LINUX ENTERPRISE SERVER 10 - INSTALLATION AND ADMINISTRATION 11-05-2007, Installation Manual

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For More Information
Additional documentation and help on ACPI:
•
http://www.cpqlinux.com/acpi-howto.html
(detailed ACPI HOWTO,
contains DSDT patches)
•
http://www.intel.com/technology/iapc/acpi/faq.htm
(ACPI
FAQ @Intel)
•
http://acpi.sourceforge.net/
(the ACPI4Linux project at Sourceforge)
•
http://www.poupinou.org/acpi/
(DSDT patches by Bruno Ducrot)
28.4 Rest for the Hard Disk
In Linux, the hard disk can be put to sleep entirely if it is not needed or it can be run in
a more economic or quieter mode. On modern laptops, you do not need to switch off
the hard disks manually, because they automatically enter an economic operating mode
whenever they are not needed. However, if you want to maximize power savings, test
some of the following methods. Most of the functions can be controlled with powersaved
and the YaST power management module, which is discussed in further detail in
Sec-
tion 28.6, “The YaST Power Management Module” (page 524).
The hdparm application can be used to modify various hard disk settings. The option
-y
instantly switches the hard disk to the standby mode.
-Y
puts it to sleep.
hdparm
-S x
causes the hard disk to be spun down after a certain period of inactivity. Replace
x
as follows:
0
disables this mechanism, causing the hard disk to run continuously.
Values from
1
to
240
are multiplied by 5 seconds. Values from
241
to
251
correspond
to 1 to 11 times 30 minutes.
Internal power saving options of the hard disk can be controlled with the option
-B
.
Select a value from
0
to
255
for maximum saving to maximum throughput. The result
depends on the hard disk used and is difficult to assess. To make a hard disk quieter,
use the option
-M
. Select a value from
128
to
254
for quiet to fast.
Often, it is not so easy to put the hard disk to sleep. In Linux, numerous processes write
to the hard disk, waking it up repeatedly. Therefore, it is important to understand how
Linux handles data that needs to be written to the hard disk. First, all data is buffered
514 Installation and Administration