[BBLISA] System Backup thoughts and questions...

[John Orthoefer]

Depending on how you are coping files.   Sparse file detection can  
cause files to shrink.   Most programs that detect sparse files, use  
some variant of an algorithm that works like:  if I see more than x  
nulls in a row consider this file sparse.   Which x is normally on the  
order of 512.

They do this because it's much harder to inspect the files and figure  
out based on the committed blocks and the file size if a file is  
sparse and it's got the added benefit that it can give you some  
compression.   So even though it might get it wrong from time to time  
there is no harm and it works with all "Unix" filesystems without  
having to know the details of how the filesystem works.

As for the limit on inodes in cp.   Make sure you are reading the  
about YOUR version of cp.   If he isn't having a performance problem  
with 114k files in a single directory I doubt he's running a very old  
OS.   Since it's got to have a better directory structure than just a  
linear list of files for the directory.

just my take on things.  While I wait for an rsync to finish.

johno




On Jan 8, 2009, at 5:55 PM, Daniel Feenberg wrote:
>
> I can think of reasons a filesystem might grow as it was copied,  
> such as hard or soft links on the source, or sparse files on the  
> source, but it is harder to think of reasons for a filesystem to  
> shrink.

-------------- next part --------------
A non-text attachment was scrubbed...
Name: smime.p7s
Type: application/pkcs7-signature
Size: 2210 bytes
Desc: not available
Url : http://www.bblisa.org/pipermail/bblisa/attachments/20090108/ac82a02e/attachment.bin