Documentation on ext3?

[jc at trillian.mit.edu (John Chambers)]

Due to some serious performance  problems  on  a  server,  I've  been
trying  to  find  information  about  how  the "journaling" ext3 file
system works. I haven't found much.  In the "man fs" page we find the
statement:

   ext3   is a journaling version of the ext2 filesystem. It is easy to
          switch back and forth between ext2 and ext3.

This isn't very helpful.  If you don't know how to do it right, being
told  that  it's  easy  is  not  very helpful.  In the RH systems I'm
dealing with, I've found nothing further on the topic.

The basic problem I'm looking at is that the machine will be chugging
along,  happily running a bunch of processes.  Then suddenly they all
slow to a crawl, something like 10 to 100 times  slower.   There  are
delays  of a minute or more in things like writing a tiny file.  When
this happens, top shows that  the  processes  called  "kupdated"  and
"kjournald"  have jumped to the top of the cpu-usage list.  Sometimes
kswapd is also up there, but usually not,  so  the  problem  probably
isn't swapping.