Date:	Fri, 11 Apr 2008 00:36:45 +0200
From:	devzero@....de
To:	lkml@...anurb.dk, pernegger@...il.com, tvrtko@...ulin.net
Cc:	linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: Western Digital GreenPower drives and Linux

i also have such a drive (damn, if i knew that saving some Watts would hurt...) - and i measured ~100 load_cycle_count per hour, which is _way_ to much, imho.
if we trust the spec, the disk would be dead after ~1year.

it seems that "intellipark" is not that intelligent as it should be and a little bit too agressive.

from what i have found, the time for parking the heads is much below the linux kernel flush interval (which seems to be at 30secs),  so i think the best thing to do is tuning either dirty_expire_centisecs and dirty_writeback_centisecs  (defaults to 3000/500 on my system)  or tune the disk parking interval , so that the disks own interval is greater than the linux flush interval.

i also openend an SR at WD - will see if they will recommend that dos utility, too.

>I got back from WD's tech support and received a DOS utility which can control 
>this drive feature, apparently using vendor specific commands. With it head 
>unload timer can be disabled or set to a period between 100ms and 25.5s. 

doh - so that disk always is faster with parking it`s heads than linux default flush interval !?
btw - is that dos utility available for download somewhere?

regards
roland



List:       linux-kernel
Subject:    Re: Western Digital GreenPower drives and Linux
From:       "Tvrtko A. Ursulin" <tvrtko () ursulin ! net>
Date:       2008-04-10 7:48:08
Message-ID: 200804100848.08442.tvrtko () ursulin ! net
[Download message RAW]

On Wednesday 09 April 2008 21:18:35 Tvrtko A. Ursulin wrote:
> I got one of them (WD5000AACS) recently and to my horror after less than
> three days of being power on this is what I saw:
>
> 9 Power_On_Hours       0x0032 100 100 000 Old_age Always  - 66
> 193 Load_Cycle_Count 0x0032 197 197 000 Old_age  Always  - 10233
>
> At this rate the disk would reach it's design limit for load/unload cycles
> in around 80 days. Not good - so I implemented a lame workaround of keeping
> disk busy every couple of seconds - hopefully that won't kill it sooner
> that unloads would..
>
> I am also currently talking with first line of WD's tech support trying to
> get some data on how exactly those drives manage head unloading, but that
> may not lead anywhere useful.

I got back from WD's tech support and received a DOS utility which can control 
this drive feature, apparently using vendor specific commands. With it head 
unload timer can be disabled or set to a period between 100ms and 25.5s. 

Of course I asked for more than a DOS utility, but the question really is how 
was this feature intended to work with Windows for example, is there 
something there which would prevent such rapid load/unload cycle growth, and 
why isn't it documented somewhere?

I am kind off hoping that someone from WD is reading this list and will notice 
this in case my effort with tech support fails.

Tvrtko
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