[CentOS] debugging RAM issues

Wed Mar 14 19:35:40 UTC 2012
John R Pierce <pierce at hogranch.com>

On 03/14/12 12:16 PM, Les Mikesell wrote:
> If you were running software RAID1 on that box, don't trust anything
> on the drives now.   Maybe even if you weren't, but it is especially
> weird when alternate reads randomly revive bad data that you thought
> had been fixed already.

and the worst part is, even if you found mismatching blocks on the 
mirrors, there's no way to know which one is the 'good' one, as there's 
no block checksumming or anything like that with conventional RAID.

this is a major reason I *insist* on ECC for any sort of server other 
than a lightweight home system.   ECC memory will detect bit failures so 
you KNOW something is funky.

this is also a major reason why RAID is *not* a substitute for backup, 
its ONLY about availability.

john r pierce                            N 37, W 122
santa cruz ca                         mid-left coast