Hi, Tony,
I'm not sure of the benefits of ReiserFS other than journalling, but I can
give you a quick overview of journalling itself:
Basically, journalling is a way of ensuring that the file system never (in
theory, at least :) ) becomes internally inconsistent. For instance, if you
were running Win9x with [VFAT, FAT32] or Linux with e2fs and you poked your
reset button, the part of the file system that is in charge of writing
everything to the hard drive wouldn't get a chance to flush it's buffers,
make sure all of the file allocation tables/inodes were pointing at valid
files, and so on. When the system comes back up, you will have to sit
through a scandisk in Win9x or an e2fsck in Linux while the OS goes through
and sorts out all of the potential problems with the file system and fixes
them.
Now with Reiser FS (NTFS for WinNT/2000 and BeFS for BeOS are journalled as
well), prior to each file system write to the hard drive, the system
basically does a pre-write to a special file called a journal file that
says, "I intend to write the following information to file FOO: xxxxxxxxxx".
Once the entry is verified to be in the journal, the system applies the
change to the actual file and finally removes the entry from the journal and
marks it as being completed. This way, the system has two choices in case
of a catastrophic shutdown: if there are any entries in the journal file
that are marked as incomplete but valid, the system can apply those updates
without compromising the integrity of the file system, and it will do so.
However, if the system was interrupted in the process of writing to the
journal file itself, the entry will be invalid and will be deleted without
being applied. Either way, the actual file system itself remains valid and
internally consistent. This is why, if you are running one of the three
file systems mentioned above, if you hit the reset button, when the OS comes
back up, there will be no file system check of any sort (in ReiserFS you'll
see a message to the effect of "applying N changes".
Granted, this was a bare bones overview, (and may not be completely
accurate: I've never dug into the source for any of the file systems in
question), but this is at least the concept.
Hope this helps,
Brian
----- Original Message -----
From: "Tony McGee" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Friday, 18 August, 2000 09:34
Subject: [expert] reiser fs ? (was: Unexplained crashes)
>
> Can anyone give me the 10c guide to what the reiserfs provides that ext2
> doesn't? I've heard the term journalling thrown about but have no idea
what
> that means. I always hate when the bandwagon is a mile down the road
before
> I've even noticed it. :)
>
> Tony
>
> On Fri, 18 Aug 2000, Roan pushed some tiny letters in this order:
> > Thanks, that took care of the problem! I just reseated all the cables,
> > memory SIMMs, and the CPU. The box has been up and running since
> > yesterday afternoon with no hiccups. Now I get to re-install and use
> > ReiserFS. :)
> >
>
