Load_Cycle_Count around 200, 000 in Inspiron 1505 I bought in June.

Rob Landley rob at landley.net
Fri Nov 2 17:39:10 CDT 2007


On Wednesday 31 October 2007 4:25:43 pm Mikael Nilsson wrote:
> As a data point, I'm NOT seeing this with my XPS M1710 laptop, with a
> new Hitachi Travelstar 7k200 (HTS722020K9SA00).
>
> After a few days of usage, the count is 139, and I can't see it
> increasing during use.
>
> This is a new gutsy install.

>From what I've been able to piece together (and I am _not_ an expert on this 
just a concerned individual with access to the internet), it's a combination 
of the BIOS and the hard drive.  Some bioses don't put disks into power 
saving mode by default.

Ubuntu doesn't touch this unless you manually go in and change a config 
setting in a text file (at which point Ubuntu actively encourages stupid 
behavior).  I have no idea what Windows does.

I've seen several places that say Hitachi drives have especially stupid 
default values which park the heads 3 times per minute, and that it's harder 
to trigger this problem with other brands of disk.  Not having other brands 
of disk handy to confirm with, I can't tell if this is true.

Also, as far as I can tell, if the "park the heads" timeout falls much below 
3x/minute, it'll never happen on Ubuntu because Ubuntu touches the disk that 
often anyway.  (After all, something has to _unpark_ the heads often for this 
to be as much of a problem).  So Ubuntu isn't exactly blameless, either.

Note that this isn't the same as "spin down the disk".  Parking the heads is 
something that the disk can do maybe 600,000 times safely, and up to twice 
that unsafely.  The failure figures I've seen reported (admittedly anecdotal) 
start at a little over 600,000 head parks and go up to 1.2 million before 
actual failure.  How many bad sector relocations this involves I dunno.  I 
suspect the 1.2 million was a mostly read-only disk that was doing a lot of 
retries (and thus very slow but not failing, because it wasn't corrupting 
sectors with misaligned writes), but that's just a guess I can't confirm.

(I miss my old thinkpad that only parked the heads if the built-in 
accelerometer detected the sucker was falling or bumped...)

Rob
-- 
"One of my most productive days was throwing away 1000 lines of code."
  - Ken Thompson.



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