Journaling.

[Theodore Ts'o]

On Mon, Dec 27, 2004 at 12:04:51PM +0530, Gogulamudi, Basa Mallika wrote:
> Hi,
> 
> 	I am using ext3 file system. Can I know the place where
> journal log is stored and more details about journaling.

The journal is normally (there are some exceptions, such as when a
journal is created on a mounted filesystem via tune2fs) stored in a
hidden inode, inode #8.  How the journal works is that metadata blocks
that need to get modified first get written to the journal, followed
by a commit block, and only then do the modified metadata blocks get
written to their final location on disk.  If the system crashes, the
journal gets replayed either when the filesystem is mounted (in the
case of the root filesystem), or when fsck is run on the filesystem.
The reason why we run the journal as part of fsck is that it allows
the journal to be run in parallel across multiple disk spindles, to
speed bootup times.

If you want more details than this about how journalling works, I
suggest you ask specific questions.  "More details about journalling"
doesn't make clear what you already know, and what you're hoping to
learn....

						- Ted