concerned about ext4 FS

[a2ms]

Hi

I was happy to see that F11 was the first distro to come with ext4 by default, but then I found this post and I'm no really sure what to think of it. Should we really be using ext4? Please check this article I found and tell me what you think:

http://www.h-online.com/open/Kernel-developers-squabble-over-Ext3-and-Ext4--/news/112937

[kevmif]

Effectively Torvalds is saying that EXT4 writes data containing information about data (metadata) before it writes the existing data which in the case of a computer crash / power outage / whatever can leave the file system in a silently incomplete state (because the metadata exists the FS thinks that the data is there and hence an error will only occur when that data is next accessed. The plus side is some serious speed improvements within the filesystem.

I think that is correct anyway!

What this means in real world situations will vary considerably depending on the application of the FS. Would I use it on my desktop? Probably not! I would want a system that is highly tolerant of power failures. On the laptop I don't care as the system should never drop out unexpectedly.

The other point to mention is it looks like you have full control over if the FS writes the metadata first or the actual data payload first.

Torvalds is also saying that with EXT2 any problems with the FS were easy to detect, but now corruption can be a lot harder to detect (silent corruption).

I'm not a FS expert by any stretch, but I think Torvalds raises some valid points and more discussion without the stupid comments and flaming. I think the comment "Whoever came up with this solution", he concludes, "was a moron, no ifs, buts or maybes about it." is quite petty and someone of Torvalds standing should be a little more diplomatic or face losing respect.

[a2ms]

Would I use it on my desktop? Probably not! I would want a system that is highly tolerant of power failures. On the laptop I don't care as the system should never drop out unexpectedly.

I think that when we have speed vs security, security is more recommended. Why would I want the fastest FS if that has a bigger probability of losing files in any unexpected accident. Even with laptop you may run out of battery unexpectedly.. r what if the battery itself fails... The what would you say is an adecuated real life applicateion for ext4 ?

[kevmif]

Well my laptop is hardly mission critical!
Its not like it would slaughter the whole filesystem anyway. So yes, I would risk it :)

On a mission critical system or a personal machine of high value (need it everyday, lots of important data) I would definitely steer clear of it.

[bsund]

I did manage to get the zeroed out files bug on Fedora 10 using ext4, I'm not sure if Fedora 11 have those patches to prevent it.

And that ext4 is a bit lazier to write down stuff is for performance and doesn't have anything to do with the zeroed out stuff.

I think the zeroed out files is because most software is made with ext3 in mind, which writes to disk each 5 seconds, so the software zero out the original file but doesn't flush the data to disk correctly.

[hephasteus]

Jump on the DC computers with huge deep cycle batteries bandwagon.

http://www.mini-box.com/DC-DC;jsessionid=0a0108421f43c409b9c09b5644acb182beb2 4e606a6e.e3eTaxePaNqNe34Pa38Ta38Oa3j0

http://www.abra-electronics.com/products/catalog/BP1210-Samlex-10-Amps-Battery-Charger-with-PFC-p-5779.html

Big dirty cache's and days long UPS for everyone.

[Zlobniy Shurik]

I lost about 2Tb data on raid formatted with ext4 on Fedora10.

Hardware state of raid was OK. It was software problem (many files got file-length equal 128Tb and was unreadable).

Now I use only ext3 and have not any problem.