[ale] dd & unexpected soft update inconsistency, HUH ?

[Courtney Thomas]

Thank you for your help Greg.

I should have stated that I'm running for my network gateway server a
linux compatible version of FreeBSD-5.3, hence UFS not XFS.

I should have also said that my former mirroring was under 4.3 not 5.3
FreeBSD, again, with it's attendant linux compatibility.

Still, knowing all the above, it's incomprehensible that only /usr would
be corrupted in some way.

Cordially,

Courtney


On Fri, 2005-04-15 at 08:36, Greg Freemyer wrote:
> On 4/15/05, Courtney Thomas wrote:
> > I've been using dd for years to mirror my server HD without problems.
> > 
> > The command used is:    dd if=< original HD > of=< mirror HD >
> > 
> 
> I don't fully understand why, but with mounted filesystems this was
> known to cause filesystem corruption with XFS in the not too distant
> past.
> 
> i.e. directly accessing the block device underlying a mounted XFS
> filesystem caused filesystem corruption due to incompatible buffering
> issues between the direct block access and the XFS filesystem access.
> 
> I'm almost positive that even read-only access like the above
> triggered the issue and is why it was considered a significant
> problem.
> 
> I don't know if any other Linux filesystems shared this issue, nor do
> I know if it was ever resolved in XFS.  I don't even remember if this
> was 2.4 or 2.6.
> 
> Greg