Re: [gentoo-user] Re: [OT] fast recursive local copy

[Volker Armin Hemmann <volkerarmin@googlemail.com>]

On Freitag 14 August 2009, Joerg Schilling wrote:
> Dirk Heinrichs <dirk.heinrichs@online.de> wrote:
> > Am Freitag 14 August 2009 10:50:45 schrieb Joerg Schilling:
> > > Note that on Linux you may need to add "-no-fsync" because file I/O is
> > > slow on Linux. On Solaris, not using -no-fsync slows things down by
> > > aprox. 10% but allows star to grant that everything was really copied
> > > to stable storage. On Linux, ot using -no-fsync slows things down by
> > > aprox. 400%, this is why I recommend to add "-no-fsync".
> >
> > This is also quite interesting. Do you have some (links to) recent
> > benchmarks which would second that? Could this even be depending on the
> > filesystem used on Linux?
>
> I did this test aprox. 3-4 years ago. You may try to do an own test and
> report.
>
> I did just rerun a test on a recent ubuntu in a VirtualBox environment and
> the speedup factor with -no-fsync was 8x.
>
> Jörg

reiser4 on raid5, compression is on, since no barriers, sync mode. Three runs, 
first without, second with, third without -no-fsync. echo 1 > 
/proc/sys/vm/drop_caches in between each run. temp was removed and recreated 
between each run. source and target on different md devices.

star: 0 blocks + 96006656 bytes (total of 96006656 bytes = 93756.50k).                         
star -copy -p -xdot -acl -sparse -C /usr/local/portage . temp/  0,85s user 
16,79s system 6% cpu 4:48,77 total 

star: 0 blocks + 96006656 bytes (total of 96006656 bytes = 93756.50k).
star -copy -p -xdot -acl -sparse -no-fsync -C /usr/local/portage . temp/  
0,43s user 3,14s system 24% cpu 14,389 total


star: 0 blocks + 96006656 bytes (total of 96006656 bytes = 93756.50k).
star -copy -p -xdot -acl -sparse -C /usr/local/portage . temp/  0,88s user 
15,93s system 6% cpu 4:13,76 total
  
but reiser4 is infamous for not loving fsync ;)