[CLUG] ext3

[Harry J Walsh]

>>>>> "Peter" == Peter Flynn <peter at silmaril.ie> writes:


    Peter> ext3 is journaling. You need more disk space for it but I
    Peter> read somewhere recently (/.?) that it is much better than
    Peter> ext2.

I don't think you need that much more disk space.  

ext2 and ext3 are identical on disk.  You don't even have to run a
conversion tool to switch between them.  The differences are at the
layer just below vfs where writes and reads are imlemented.

Journaling is basically a two phase commit process.  In ext2 if the
system dies during a write, then the filesystem will be left in a bad
state.

In ext3 the write is to th journal.  If the system crashes while
writing to the journal, then the transaction can be aborted atboot up, 
leaving the filesystem error free.  

The journal is committed to the filesystem periodically, but the
transaction isn't removed form the journal until it is completed on
the filesystem.  If the system crashes during a journal flush, then
the recovery process can look at the journal and undo all partially
committed transactions and start a gain.

So ext3 is slightly slower ( some say negligible ), and requires the
overhead of a journal per partition.

I think it's worth it.  However, I'm not going to upgrade to it on any 
critical systems for another while yet.

--
hjw