Preventing the nightly backup from disturbing the cache

[steve at rueb.com (Steve Bergman)]

David Mansfield wrote:

> I don't think this is necessarily safe to do.  O_DIRECT adds 
> additional requirements to the memory buffer's alignment and file 
> position alignments.  Unless you have audited the 'tar' source code, I 
> think this is a bad idea.

Actually, I was just getting ready to follow up.  Although the tar 
archive structure looks fine, and most of the files are OK, I HAVE FOUND 
CORRUPTION IN SOME FILES.  So don't use that patch.

OK.  If that strategy does not work, how about the earlier suggestion of 
fadvise?  Would that be safer?  And can anyone provide an example of how 
fadvise64_64() is actually used?  I'm not a C programmer.

-Steve