[ILUG] hard drive workouts - any ideas?

[Ivan Griffin]

This is probably getting a little off topic, but actually the reasons the 
drive don't do these workouts on their own are probably varied - from 
acoustic management, power management, lack of standardised host control 
API, performance degradation when competing with the OS for sectors...

SMART is one of those potentially useful but not sufficient 
measurements.  I'm actually hoping to prod the drive along to find 
potential errors far earlier than SMART will detect them through normal 
drive operation.  SMART predicts catastrophic failure through changing 
trends - absolute values of SMART attributes, other than perhaps 
temperature and age(s), are meaningless.  There are many defect situations 
that are not catastrophic, such as a single sector with a hard error.

Bit-rot can occur - esp. in commodity PC hardware (dodgy brown/black 
out protection, flakey cables, failing fans etc). Odd bytes of data can 
get bent out of shape, and steadily so over time - chances are ECC can 
probably correct with more confidence the earlier it comes across the 
issue.

A sector with a bad bit now can degrade over time, so I'm erring on the 
side that it is better to either refresh or remap the sector now, than to 
let it degrade further.

I don't think running across all the sectors on the drive, say, once 
every month is going to serious reduce the life of a drive that is in 
reasonable use. And if sectors have gone south on the drive, I'd like to 
know about it as early as possible with SMART to replace it.  That it the 
reason I run smartd on my boxes. Although it is probably worth pointing 
out that SMART is not something to be too dependent on, if the results of 
the google study are anything to go by.

Anyway, as you said earlier, the information I seek is proprietary and 
probably only exists within each of the drive manufacturers themselves. 
I'm going to plow on regardless with my plan anyway, in the naive hope 
that I don't think it will make things worse, and could potentially help.


Cheers,
Ivan.


On Sun, 16 Sep 2007, Gary Pigott wrote:

> I know how drives work. I've got a couple of hundred spinning away in a few 
> racks in a colo in Dublin, so my mileage is varied, but considerable ;-) What 
> I'm trying to get across is that it doesn't make a difference how long the 
> data sits on the disk in it's damaged state, as it'll be recovered eventually 
> anyway if it's a bad sector, (unless you've used up all your spare sectors). 
> Your workouts *will* repair the errors quicker, but at the expense of 
> increasing the frequency of the errors you're trying to clean up, and 
> consuming a finite resource. There's a reason why drives don't do these 
> regular workouts on their own.....
>
> Wouldn't it be better to be aware of the errors and usage of these spare 
> sectors, *without* putting extra wear on the disk? SMART attributes 01, 05, 
> 196 & 197 are for *exactly* this purpose, and mean that you don't have to 
> resort to poking around with firmware at all.
>
> Gary