[gpfsug-discuss] what's on a 'dataOnly' disk?

[Uwe Falke]

Hi Mark, 
AFAIK, there will not be any file system corruption if just data blocks 
are altered by activities outside GPFS. Mind: the metadata just tell were 
to find the data, not what will be there.

If you have the data replicated, you could compare the two replica. But 
mind: with some GPFS version, a replica compare tool was introduced which 
would fix differences by always assuming the first version it has read is 
the correct one -- which is wrong in half of the cases, I'd say. Only now 
(I think with SpSc 4.2), a version of that tool is available which allows 
the user to check the differences and possibly select the good version.

If you have your data replicated and you  may assume that the problem is 
affecting only disks in one failure group (FG), you could also set these 
disks down, add new disks to the FG and restripe the FS.

Then, GNR works with end-to-end checksumming. This would not help you 
retrieving the original content but would allow you to identify altered 
file contents.


 
Mit freundlichen Grüßen / Kind regards

 
Dr. Uwe Falke
 
IT Specialist
High Performance Computing Services / Integrated Technology Services / 
Data Center Services
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