Re: Help: very slow software RAID 5.

[Bill Davidsen <davidsen@tmr.com>]

Dean S. Messing wrote:
> I have also discovered "smartctl" and have read that if the short smartctl
> tests are run daily and the long test weekly that the chances of being
> caught "with my pants down" are quite low, even in a two disk RAID-0
> config.  What is your opinion?
>   

There's a good paper on using smartctl to predict the health of disks, 
and if you can't find it I probably have a copy somewhere, since I gave 
a presentation on RAID issues which included it. But the basic premise 
was that if you see errors of certain types, the drives are likely to 
fail soon. It did *not* say that absent these warnings the drives were 
unlikely to fail, un fact most drives which did fail did so without 
warning. So for about 90% of the failures there is no warning.

I had servers a few years ago, running 6TB/server, on lots of small fast 
drives, and I concluded that the predictive value of SMART was so small 
that it didn't justify looking at the reports. Take that as my opinion, 
assume that drives fail without warning.

I'm getting around to replying to several things you have said in 
various posts, so that people who are threading answers will be happy...

-- 
bill davidsen <davidsen@tmr.com>
  CTO TMR Associates, Inc
  Doing interesting things with small computers since 1979