I found this interessting Quote of Linus Torvalds regarding ext4:
Linus Torvalds wrote:It literally does everything the wrong way around -- writing data later than the metadata that points to it. Whoever came up with that solution was a moron. No ifs, buts, or maybes about it. At least with ext3 it's not the default mode."
More about this issue and discussion:http://www.linux-magazine.com/Online/Ne ... 3-and-Ext4
Linus Torvalds, Ted Ts'o, Alan Cox, Ingo Molnar, Andrew Morton and other Linux kernel developers are embroiled in a contentious discussion over the sense -- or nonsense -- of journaling and delayed allocation before a commit in the ext3 and ext4 filesystems. Heavy words are flying.
As it is stated there the ext3 FS writes the meta Data of the file and the file itself with a delay of 5 sek. - ext4 is delaying the writing of the physical Data up to 2 min.
For RAID-Systems this fact can lead to a complete different behavior then Single Disk Systems.
Add to this equation users (yes all of us
) and their creativity when it comes to file access scenario (iSCSI, video editing files stored on the NAS, Office Files stored on NAS (*.pst e.g.)).
So IMHO Qnap should consider to add a warning where the selection of the filesystem ist placed in the GUI or maybe where RAID ist placed. Most user would blame Qnap at this moment for something not being their fault when data corruption occurs in those scenarios.