[Hardware] [gmane.comp.freedesktop.hal] Re: hdparm, changing the hard-disk spindown (sleep time)

[Anton Farygin]

FYI.

On Tue, 23 Aug 2005 22:14:47 +0200, Danny Kukawka wrote:

> On Tuesday 23 August 2005 20:06, Richard Hughes wrote:
>> This is a very rough and ready patch.
>>
>> To finally drive a nail in the coffin for the bodge that is PowerManager
>> dbus daemon, this is a quick patch to add a:
>>
>> org.freedesktop.Hal.Device.SystemPowerManagement.SetSpindown (seconds)
>>
>> method to all hard disks. This lets us abstract the detail of hdparm
>> (and its weird ID mapping) and lets any application use the spindown
>> sleep method.
>>
>> I understand that SetLowPowerMode may do this sort of thing there, but
>> it made sense to use HAL to call a HAL method, if you see what I mean.
>>
>> Plus it gives other programs the fine-grained spindown control.
>>
>> What do ppl think? Is there an easy (cross-distro) way of calling
>> hdparm?
> 
> I'm not sure if it is a good idea to add this to HAL. It's not really
> needed for powermanagement. Harddisks have a really intelligent
> powermanagment. You lose with such solution more than you win.
> 
> Here the power consumption data for a notebook harddisk (ide/sata):
> Startup (peak, max.)		5.5W 	NC
> Seek						2.3W	2.7W
> Read (avg.)				2.0W	2.3W
> Write (avg.)				2.0W	2.3W
> Active idle (avg.)		1.1W	1.2W
> Low power idle (avg.)	0.85W	0.9W
> Standby (avg.)			0.2W	0.25W
> Sleep						0.1W	NC
> 
> * A disk on Low Power idle need less than 1 Watt per hour for a normal
> battery with 50000mWh you can let run the harddisk 50 hours. The harddisk
> is not the point to save power. You maybe win on a battery fuel maybe 1-3
> minutes (or something like this). If you would like to save power it make,
> if any, more sense to use the advanced powermanagement features of a disk.
> 
> * If you not read/write from/to the harddisk the disk regulate the disk
> down, but never shut down the device. The reason is easy: you lost more
> power with each startup than let the harddisk online somewhere between
> 'Active idle' and 'Low power idle' (depends on the
> model/manufacturer/version maybe also standby).
> 
> * Other reason to let do this the intelligent internal powermanagement of
> the disk is: the time needed to reactivate the device. You lose more
> performance than you lose power between 'Active idle' and 'Low power
> idle'.
> 
> * If you use a journaling file system: you normally need to flush
> periodically. This could run in a race between shut down device and
> restart device by system to flush. This means more power consumption as if
> you change nothing.
> 
> * Different of actual HDDs react on the usage of the disk and adapt this
> to the own powermanagement. If you engage to this process you can reduce
> the lifetime of the disc (e.g. trough unneed increase Load_Cycle_Count,
> can also be a effect in races as above) and again: lose more power than
> you save.
> 
> * And at least: the manufacturer of harddisks for notebooks know what they
> do and they optimized the devices. ;)
> 
> We had this in the past also in powersave, but we removed this because of
> the points above and trouble with some decives. And with upcomming SATA
> drives this should not work IMO (I think hdparm work only with IDE, or?).
> 
> 
>> Plus it gives other programs the fine-grained spindown control.
> Problem: What if different applications with different settings try to set
> their own settings? Not a good concept, or?
> 
> If you need more info our specialist for powermanagement and harddisks if
> back next week from holidays.
> 
> What you think?
> 
> Cheers,
> 
> Danny