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Location: Rome, Italy ; Novi Sad, Srbija; Brisbane, Australia
Distribution: Ubuntu / ITOS2008
Basic difference between ext2 and ext3 is that ext3 had journaling support. What this means is that it keeps a journal, or log of all files (data) and information about all files (metadata) and after a crash or hangup it uses that information to restore the system to its original state. This means no long file system checks, and less chance of corrupted data.
Heres a link to a more in-depth description, thats one of the results google gave me, so if you need more explanations on how journaling filesystems work search google, and if you have questions you know where to ask
Here's the link http://www.linux-mag.com/2000-08/journaling_01.html
so is the ext File system like a mini version of RAID mirrioring then?
i thought that ext2 and ext3 were both journaling file systems ?
but what happens when you delete a file, is its information and contents still in this log? or is it like the windows FAT and just delete's the files index on the disk and leaves the files contents there?
i know that the files index on a linux system is called an inode, i found that one out from some place
OK, here's a lowdown...
Ext2/3 use inodes. Every file is assigned an inode. When you delete the file, so long as nothing else is written to the disk, then you can still recover the inode, and so recover the file. However, this is unlikely since things are being written to disk all the time - you'd have to be pretty lucky to undelete files. Most programs in Linux that edit files will, by default, save a backup copy of the file, prior to it being editted, as file~.
Journalling is only really a measure to ensure that things are not lost completely during a crash. Without journalling, should you have a crash, the best you could hope for is that you have a fairly lengthy filesystem check (fsck) and you may lose a couple of files. At worst you will have a screwed filesystem and you're in trouble. With journalling, should you have a crash, you may occasionally get a quick fsck to make sure that everything is in order, otherwise the files are simply updated (or should that be downdated?) to their previous state.
I'm not sure whether deleted files can be recovered through journalling, but I wouldn't have though so... their inodes are likely to have been used again already.