Re: Linux Software RAID a bit of a weakness?

["Colin Simpson" <csimpson@csl.co.uk>]

On Mon, 2007-02-26 at 08:56 -0800, David Rees wrote:
>
> > You could configure smartd to do regular long selftests, which would
> > notify you on failures and allow you to take the drive offline and dd,
> > replace etc.
> 
> So what do you do when your drives in your array don't support SMART
> self tests for some reason?
> 
> The best solution I have thought of so far is to do a `dd if=/dev/mdX
> of=/dev/null` periodically, but this isn't as nice as running a check
> in the later kernels as it's not guaranteed to read blocks from all
> disks. I guess you could instead do the same thing but with the
> underlying disks instead of the raid device, then make sure you watch
> the logs for disk read errors.
> 
> -Dave

SATA isn't supported on RH 4's SMART.

If I say, 

dd if=/dev/sda2 of=/dev/null

where /dev/sda2 is a component of an active md device.

Will the RAID subsystem get upset that someone else is fiddling with the
disk (even in just a read only way)? And will a read error on this dd
(caused by a bad block) cause md to knock out that device?

Thanks

Colin

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