On Fri, May 13, 2011 at 05:32:05AM -0700, obviously wrote:
> Hello,
> 
> I have a question I can't solve...
> 
> The is the situation:
> 
> I create a file with: dd if=/dev/urandom of=test.bin bs=10M count=300
> This gives me a file of 3GB.
> I check it's MD5 with md5sum test.bin
> 
> I clear my cache with echo 3 > /proc/sys/vm/drop_caches.
> 
> I check my chache with free -m.
> 
> I start a backup with Bacula of only 1 file, namely test.bin
> 
> Again, I flush the cache and when the back-up job is starting I remove the 
> test.bin file on the server.
> 
> And Bacula doens't react at all, it keeps backing up the file like it is 
> still there.
> 
> The backup finishes with no warnings, even it is removed during the backup.
> 
> I restore the test.bin file from tape and checks the md5 of it, and strangely 
> the md5sum is the same... 
> 
> So my question, how does Bacula do this? Cause I remove the file during the 
> backup and flush the cache frequently...
> 
> I hope you guys understand my q, my english is realy bad :) excuse me...

I would have thought that it is because the space isn't really reclaimed until
all open file descriptors are closed. Repeat the experiment and run 'df' at
these times (assuming that bacula is saving to a different filesystem):

a) before the file is created
b) after the file is created, while bacula is backing it up
c) after the file is deleted, before bacula is finished
d) after bacula has finished


a) will have low space usage
b) will have higher space usage
c) will have the same as (b)
d) will have the same as (a)



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Achieve unprecedented app performance and reliability
What every C/C++ and Fortran developer should know.
Learn how Intel has extended the reach of its next-generation tools
to help boost performance applications - inlcuding clusters.
http://p.sf.net/sfu/intel-dev2devmay
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