[sf-lug] semi-OT: help with dying disk

Rick Moen rick at linuxmafia.com
Sat Mar 15 03:28:35 PDT 2008

Quoting matt.price at utoronto.ca (matt.price at utoronto.ca):

> the hard drive in my laptop is dying, with messages of this ilk:
>    so as regards recovery

See, I'd not actually heard of GNU ddrescue, so hats off to Asheesh, for
suggesting it.  (Me, I just try to use good disks, avoid heat buildup,
use decent PSUs, do occasional backups, and mostly just hope for the best.
Customer data gets better treatment, but it's the old "cobbler's
children go barefoot" problem at home.)

> then i have a second one, regarding a new disk.  from the looks of it,  
> $150 will now buy either 200 gigs of 7200 RPM  2.5" disk, or 250 gigs  
> of 5400 RPM.  any idea how the speed difference is likely to affect  
> both speed and power consumption on my laptop? 

Well, quite seriously, at least potentially.  Mutatis mutandis, a drive
that spins 33% faster will draw about that much more power and put out
that much more heat.  OTOH, speed ratings of laptop hard drives (exactly
as with so-called "48x" CD drives) are a bit misleading, because of
measures to keep them spun down a high percentage of the time.

> this is a dell d820  laptop with a core duo cpu, so it's fairly quick
> by my standards, but  of course i wouldn't mind it being faster;
> however, it's also a  terrible power hog under linux, currently (with
> what i believe is a  5400 rpm disk) barely staying up for an hour on
> battery power.

Gee, you might, at that sort of battery duration, want to check with
other d8x0 users running Linux, because that sounds awfully slim.  Maybe
you might even need a new battery?  Lithium ion cells do lose their
capacity progressively over the years, whether you use them or not.
The only cure, really, is to buy a replacement battery.

I did this (bought a replacement, new battery) with my 800MHz G3 PowerPC
iBook 2.2 (running Xubuntu), and it now gets many hours of runtime on
battery alone.  

Of course, I notice that machines more recent than that now-antique
machine's era seem to have taken a big leap in CPU power consumption, so
I might have just found a sweet spot.

> so i wondered, any comments on the likely speed/power tradeoff, and
> also any hints about increasing disk lifetime?

One factor that feeds into disk lifetime is heat.  As long as your
system is able to conduct or convect any generated heat away quickly
enough, no problem (although it's of course better to not generate that
heat in the first place, if you can avoid doing so).  However, if your 
fans and fins aren't keeping up for some reason (hot day, blocked heat
vents, etc.), then you get runaway conditions -- heat buildup.  

Heat buildup kills electronic components, and especially those on hard
drives, more surely than just about anything else can.

You'll notice that I haven't given you any easy, clean, bankable answers
in the above.  To my knowledge, there aren't any -- just a bunch of
general principles that might or might not help you over the long run.

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