Re: Backup System

[Chen Wei <weichen302@gmx.com>]

On Fri, Feb 03, 2012 at 09:35:02AM +0000, Jon Dowland wrote:
> I'd recommend avoiding rsnapshot as hard-link trees just don't scale
> and cause filesystem metadata problems.
> 
> I wrote about my present thoughts on backups in December:
> http://jmtd.net/log/backup/

I have used backintime for almost one year. Since it use hardlinks to
save space and also because I use hardlinks to remove duplicated files,
I am little bit concerned. I did a test on reading a directory with a
lot of small files. There isn't any noticable difference between read
one copy of that dir and one thousand hardlinked copies of it. Could it
possible something else slows down your system?


the test in detail:
Squeeze AMD64, running Kernel 3.2.1, the test directory contains 18K+
maildir files of Debian-User mailing list, stored on XFS filesystem with
default mount options.

after drop the cache by "echo 3 > /proc/sys/vm/drop_caches", timing a
script which read mail file and parse mail header. It takes around 36
seconds to read and parse all files. Then make 1000 hardlinked copies of
that directory, now the output of "ls -l" looks like

-rw------- 1001 wei mail 4836 Feb  3 20:30 1328272212.M[....]en,S=4836:2,S

It still take around 36 seconds to run.



-- 
Chen Wei