Re:10-15% (Score 1)

> It's dog slow since all data needs to be written on disk twice, once to the file and once to the journal, but at least it keeps your data intact well.

This is in theory but in some setups data=journal mode can actually be faster than all of the other Linux journaling FS and ext2. Please refer to:

http://www-106.ibm.com/developerworks/linux/libr ar y/l-fs8.html