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Re: Ext3 strangeness data loss



> As I said earlier, it's probably a hardware problem, or perhaps a
> combination of hardware and kernel (i.e., the kernel tries to be too
> agressive with the IDE DMA configuration, as Stephen conjectured).
> 
> > > In any case, the scenario I described (a controller/cable problem, or
> > > an incorrectly configured IDE DMA settings) are all still possible
> > > with RAID; RAID does not help you prevent these sorts of problems.
> > 
> > It's SW RAID-1, disks are on the same controller,
> > but different buses / cables.
> > Am I right, that in this case HW errors are *very* unlikely?
> > That would mean that there are exactly the same bits of errors at exactly
> > the same time on different cables/disks...
> 
> Nope, you're incorrect here.  When you read from a SW-RAID-1 array,
> the Software Raid driver picks one or the other disk (whichever one is
> available) and reads from the that particular disk.  It does *not*
> read the block from both disks, and compare the blocks read from both
> disks to make sure they are identical, as you seem to believe.

Yes, I did believe that.
So only one more question (and answer) would be usefull for all of us:
Do You know about if there is a mode switch for RAID-1 setup (my case is
evms-raid) to do this comparision?
This makes sense as an option for debuging and for high availability
production also.

viktor





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