Posts Tagged ‘ext4’
Ext4 data loss
By chys on March 19th, 2009I, too, have experienced data losses in ext4 partitions.
There was some problem with my X that hangs the system about once a week (I was upgrading my X system and drivers too aggressively) so sometimes I had to hard reboot my computer (even magic SysRq does not respond in such cases). I lost most or all of my KDE settings after the reboots, and for one time also all my Thunderbird settings. This never happened until I migrated to ext4..
So I converted all my ext4′s back to ext3 and downgraded the kernel to 2.6.27 which is considered by Gentoo as stable. Loss of KDE settings is no big deal, but I really don’t want to have a kernel bug erase my codes, or homework that is due tomorrow, or diary I’ve kept for eight years.
Anyway, the performance of ext4 is really good..
References – Other recent reports of ext4 data losses:
[1] https://bugs.edge.launchpad.net/ubuntu/+source/linux/+bug/317781/comments/45
[2] http://www.h-online.com/open/Ext4-data-loss-explanations-and-workarounds–/news/112892
[3] http://www.h-online.com/open/Possible-data-loss-in-Ext4–/news/112821
[4] http://cookinglinux.cn/ext4-lose-data.html (Chinese)
Migrating to EXT4
By chys on December 30th, 2008Ext4, the successor to ext3 which was formerly known as ext4dev, is marked stable in Linux kernel 2.6.28, meaning the Linux kernel team now recommends using ext4 in production.
To convert a file system from ext3 to ext4, use
tune2fs -O extents /dev/DEV
and remount the file system as ext4. (Two e2fsck runs are recommended before and after tune2fs.) Some documentations also include the -E test_fs option. This is not necessary now since ext4 is no longer experimental.
Finally do not forget to modify /etc/fstab.
An ext4 file system created this way is not a “true” ext4 – the extents feature, the main advantage of ext4 comapred to ext3, is not automatically applied to old files. New files created afterwards are in the extents format.
Unlike the 100% backward compatibility of ext3 with ext2, an ext4 file system can no longer be mounted as if it were an ext3, unless the extents feature is disabled. (If you want to disable extents, why not simply use ext3?)
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