Re: Ext4 and the "30 second window of death"

From: Tomasz Chmielewski
Date: Sun Apr 05 2009 - 14:14:03 EST


The replace-via-truncate and replace-via-rename workarounds are there
for the benefit of KDE, and GNOME, which in some configurations
apparently will replace hundreds of dot files when the desktop is
started up, for no reason that I can understand. (Not such a great
idea for SSD write endurance!) Some people apparently spend hours
making sure that their windows are exactly positioned the way they
want it when their desktop starts up, and if the system crashes while
their desktop is starting up, those they could lose their window
positions, which apparently made a whole bunch of users cranky. In
practice, most of the editors that I'm familiar with have been around
for a while, have needed to make sure that that cases such as yours
wouldn't result in data loss, and so are pretty good about using
fsync() so that users' files wouldn't be lost, no matter what the
filesystem or operating system being used.

Its more than losing window postions. I've been using ext4 with kde 4.2.1 along with some experimental modules (drm for xorg for r600 support, btrfs) and a few patches. As expected this has caused a few crashes. I have had kde lose desktop setup info (eg. it forgot it was using xrender accel). I have also had kmail lose all its configuration - which is a pita to rebuild. Note that these crashes occur long after kde has been started...

I've lost contents of my /etc/shadow file some time ago.
Great fun after reboot.

But it also means that the problem begins not with KDE and Gnome, but much, much earlier.


--
Tomasz Chmielewski
http://wpkg.org
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