Comment 660 for bug 59695

On Mon, Jan 05, 2009 at 01:41:28PM -0000, Noel J. Bergman wrote:
> I see that the new value is 254 from 128. An earlier suggestion had
> been 192, which seemed to work for me as well. Can anyone comment on
> the consequence of 192 vs 254? All that I have come across so far is
> http://ubuntuforums.org/showthread.php?t=837308 and a separate comment
> over at RedHat about 254 not working on one person's system
> (https://bugzilla.redhat.com/show_bug.cgi?id=382061#c14).

The description in the hdparm manpage is:

       -B Set Advanced Power Management feature, if the drive supports it.
              A low value means aggressive power management and a high value
              means better performance. Possible settings range from values 1
              through 127 (which permit spin-down), and values 128 through 254
              (which do not permit spin-down). The highest degree of power
              management is attained with a setting of 1, and the highest I/O
              performance with a setting of 254. A value of 255 tells hdparm
              to disable Advanced Power Management altogether on the drive
              (not all drives support disabling it, but most do).

With respect to this bug, 192 and 254 should be equivalent. 254 is
otherwise the closest approximation to 255 on systems that don't support the
255 option. (In theory, it might always be best to call hdparm -B 254
followed by hdparm -B 255, for compatibility; but that's not a change that
belongs in this SRU, either.)

I've not heard any other reports of 254 not working. As you can see, it's
documented in the manpage itself that 255 is not always supported, but I
have no reason to think 192 provides better compatibility than 254.

> By the way, Steve, did you also just fix Bug 199094?

I don't know that I would consider this a fix for 199094. It at least works
around the most significant problems described in that bug.

On Mon, Jan 05, 2009 at 03:14:33PM -0000, Adam Porter wrote:
> Do you mean that laptop mode has other, undesirable consequences that
> should be avoided by default?

Yes; there is in-line documentation in laptop-mode-tools to the effect that
enabling it causes some machines to hang on boot, at least historically; so
that's not a default that should be changed in SRU. (Even if we didn't know
of any major regression potential, turning on laptop-mode by default would
be the wrong way to fix this in SRU.)

> Do you know how it will be solved in Hardy without laptop mode?

Using the version of acpi-support that I've uploaded to hardy-proposed,
which should be available for download once another member of the ubuntu-sru
team has a chance to process it.

> Sorry for the questions. I'm not sure if this is enough of an issue
> for my laptop that I should enable laptop mode all the time, but I
> think it's worth keeping an eye on it. The SMART value's percentage
> is not changing that quickly, regardless of the raw value. I'm not
> fully convinced, with the variations in individual drives, that anyone
> really knows what the best solution is. But if you have advice, it
> would be appreciated. I will probably be staying with Hardy for a
> while.

Unless you have reason to think the load cycle count on your drive is
dangerously close to failure, I would probably advise waiting for the
acpi-support package to become available in hardy-proposed and install that.

--
Steve Langasek Give me a lever long enough and a Free OS
Debian Developer to set it on, and I can move the world.
Ubuntu Developer http://www.debian.org/
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