Renato S. Yamane wrote:
> Bart Samwel wrote:
>> Note that that should be 254. 255 gives undefined behaviour for lots of
>> hardware.
>
> 254 don't fix the problem (Load_Cycle_Count still increasing).
Even if you do it and do nothing else, so that nothing runs laptop mode
tools and/or acpi-support?
> And check below:
>
> # hdparm -B 254 /dev/sda
> /dev/sda:
> setting Advanced Power Management level to 0xfe (254)
>
> # hdparm -B 255 /dev/sda
> /dev/sda:
> setting Advanced Power Management level to disabled
>
> So, I really think that correct is 255. What you think?
Nope, 254 is correct for this. 255 means "do what you want", 254 means
"do as little power management as possible". For many drives "disable
power management" does the same as 128 (the default).
>> Here's a question to everybody here: does the load cycle count increase
>> quickly *while you're on AC*?
>
> - When I run in AC, Load_Cycle_Count never increase.
> - When I run in battery, Load_Cycle_Count increase at least 1 time
per minute. No more than 2 times per minute.
Ah, it works exactly as designed then!
>> The theory is that nobody works on battery 24 hrs/day, and that HD
>> power management actually has benefits while working on battery.
>> We've calculated that with this solution, even with very mobile usage
>> patterns your drive should live for years. If the load cycle count
>> increases while you're on AC, then the solution is broken.
>
> Yes, when I'm running in AC, Load_Cycle_Count don't increase in my
laptop.
> Messias, and in your laptop?
>
> And... Messias can hear this sound when Load_Cycle_Count increase:
> <http://bugzilla.kernel.org/attachment.cgi?id=8777&action=view>
>
> This can be a different bug?
I don't have sound so I can't see if this is the same. On my laptop it
gives a pretty loud click. This is expected, this is just the sound of
the head parking.
>> If the load cycle count
>> increases only on battery, then it works as designed.)
>
> You think that is a good idea change "hdparm -B" from 254 to 255 in
my case (/etc/acpi/battery.d/90-hdparm.sh)?
>
> Because when I run as 254, I get:
> setting Advanced Power Management level to 0xfe (254)
>
> And when I run as 255, I get:
> setting Advanced Power Management level to disabled
No, I'd keep it at 254 if it works for you. And I wouldn't worry if the
load cycle count increases while you're on battery: you're not on
battery all day.
Here's the math again, which shows why this is safe:
8 hours on battery per day * 60 minutes per hour * 1 load cycle per
minute = 480 cycles per day.
Drives are rated for 600000 load cycles -> 600000 / 480 = 1250 days =
3.42 years.
And that's if you use your laptop on battery for 8 hours EVERY DAY for
3.42 years. Nobody does that: a typical Li-Ion battery can take 300 load
cycles before it's exhausted and needs to be replaced. So, assuming you
have a battery which can handle 8 hours (!) you'd need to be in your
5th replacement battery before your hard drive fails. Do you know ANYONE
who uses a laptop into its second replacement battery? I don't either.
So this is perfectly safe. :-)
Cheers,
Bart
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