Re: attention aux disques dur des laptops

[Frédéric BOITEUX <fboiteux@calistel.com>]

Le ven 02 nov 2007 09:47:43 CET, adminskynet <adminskynet@free.fr> a
écrit :

> ...
> Sous Linux nous avons la chance de pouvoir faire un simple hdparm pour
> solutionner le problème, dans la grande majorité des cas, sauf pour
> certains disques qui continuent quand même à parquer leurs têtes de lecture
> de façon agressive.

À ce propos, Bruce Allen, dév. de smartmontools, a indiqué que si l'on
joue avec le paramètre -B de hdparm, il est incorrect d'utiliser la
valeur 255 (qui n'a pas de résultat prévisible) :

« I think that the -B value of 255 is incorrect.  You should use 254
for maximum performance.  255 IS DOCUMENTED AS 'RESERVED' IN THE ATA/SATA 
SPECS.  THE BEHAVIOR OF -B 255 THUS IS NOT PREDICTABLE AND IT MAY HAVE NO 
EFFECT.  Also according to the ATA/SATA specs any value greater than or 
equal to 128 will 'not permit the device to spin down to save power'. So 
128 will reduce power use as much as possible but not permit spin-down.

References:
http://www.t13.org/Documents/UploadedDocuments/docs2007/D1532v1r4b-AT_Attachment_with_Packet_Interface_-_7_Volume_1.pdf
PDF page 273 Document page 253
Table 43 (and the paragraph immediately following it).

So I suggest you try some different -B values such as -B 254 or -B 128.

The hdparm man page says 'values of 255 will disable Advanced Power 
Management'.  I think this is a mistake in the man page.  According to the 
ATA/SATA specs referenced above, the value 255 is reserved and has vendor 
dependent meaning (or has no effect).
 »

Pour ma part, j'ai mis -B 254...

	Fred.