NASLite-2 uses the standard journaling mode "data=ordered". As far as the size of the journal, this is dependent on the size of the device.
I've never really paid attention to the size, when you format a drive in NL2 you should see something like this telling you how big the journal is :
Superblock backups stored on blocks:
32768, 98304, 163840, 229376
Writing inode tables: done
Creating journal (8192 blocks): done
Here's a nice explanation on the merits of ext3 with journaling.
http://puggy.symonds.net/~rajesh/howto/ext3/ext3-2.html