On Wed, Jul 15, 2015 at 11:20:55AM -0400, Austin S Hemmelgarn wrote:
>
> There really isn't much of a clear distinction between ext3 and ext4 (at
> least from an end user standpoint), other than the fact that there are some
> options that only the ext4 driver understands (like extent based
> allocation).
Yeah, the main reason why we did the ext3 -> ext4 fork was that adding
64-bit numbers required major surgery, and we didn't want to break a
lot of production users who were using ext3. But from a file system
format perspective, ext2, ext3, and ext4 are the same logical file
system. There are just multiple different implementations, which all
support slightly different sets of file system features:
* Linux's ext2
* Linux's ext3
* Linux's ext4
* Hurd's ext2
* *BSD's ext2
* Grub's ext2/3/4
The last three implementations are in fact independent ones created
from scratch. :-)
Fortunately we use the same file system support code, e2fsprogs, for
all of them, which is good since it has a very extensive set of
regression test sets for our fsck program, and we've continued adding
to it as we add new file system features.
- Ted
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