[CentOS] Preventing the nightly backup from disturbing the cache
Adam Gibson
agibson at ptm.com
Mon Apr 24 23:03:49 UTC 2006
Steve Bergman wrote:
> 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.
I wonder if the corruption has something to do with needing to ftruncate
a file if the file does not precisely end at a block boundary(as the
reference in my previous email mentions). I would have expected almost
all files to not end on a block boundary so most of them should have
been corrupt but most of them were OK you say?
>
> 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
Nice. Looks like the right solution.
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