Gentoo Archives: gentoo-dev

From: Nirbheek Chauhan <nirbheek@g.o>
To: gentoo-dev@l.g.o
Subject: Re: [gentoo-dev] Re: proj/portage:master commit in: pym/portage/dbapi/
Date: Sat, 26 Nov 2011 15:52:36
In Reply to: Re: [gentoo-dev] Re: proj/portage:master commit in: pym/portage/dbapi/ by Rich Freeman
On Sat, Nov 26, 2011 at 7:14 PM, Rich Freeman <rich0@g.o> wrote:
> isn't supported.  It is available in stable coreutils.  Some speculate > that this option could increase fragmentation (both copies will share > extents from the original file, and have some extents of their own), > but btrfs doesn't overwrite anything in-place so fragmentation is a > potential issue with any file modification (change one byte in the
Adding to your comments on this: To mitigate such issues, newer versions of the btrfs fs driver have automatic online defragmentation as well. Works quite well for moderate fragmentation. A particularly ghastly example where fragmentation issues become pathological in nature are files that are fsync()ed very frequently. A typical example are the *.sqlite files in ~/.mozilla which easily get hundreds or even thousands of fragments after a few hours worth of firefox usage (can be verified with filefrag). To fix such things, regular online defragmentation of those specific files can be done using `btrfs fi defrag <file>`. -- ~Nirbheek Chauhan Gentoo GNOME+Mozilla Team