On 02/13/2012 05:09 PM, Roman Mamedov wrote:
On Mon, 13 Feb 2012 16:40:03 +0900
dima<dole...@parallels.com> wrote:
Hello Ralf-Peter,
Actually it is possible. Check out David's response to my question from
some time ago:
http://permalink.gmane.org/gmane.comp.file-systems.btrfs/14227
The nocow.c script he attached does just the thing you want. The script
is really working. I needed nocow for different purpose but it did not
occur to me to try it on VM image and see if the performance would
improve. Sounds like a great idea. If you get around to try it, pls.
post your impressions here.
Thanks for the link, this is indeed interesting.
I made a couple of small changes, i.e. I wanted a way to unset nocow and to
check that changing flags really worked.
gcc -o /usr/local/bin/nocow nocow.c
ln -sf /usr/local/bin/nocow /usr/local/bin/cow
Perhaps the support for setting this flag should be added to the 'btrfs'
utility.
Hello Roman,
I don't seem to be able to 'unset' the NOCOW flag. Looking at the code
I would guess that it is supposed to alternate between 'cow' and 'nocow'
states, but the condition
printf("Remove NOCOW flag for %s\n", argv[1]);
never shows for me. What should I do to make it working?
Maybe it would be nice to have a switch to just check if nocow is set on
file without actually changing the flag.
thanks
~dima
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