Hey guys and gals, I did confirm that ext3 writeback mode does disable the journal sync. This greatly reduces the I/O activity with the hard drive and is faster than the ordered mode.
If I had a laptop, I would use the ext3 writeback mode. This should greatly reduce the spin up down cycles for a given duty cycle setting.
What you would give up for this advantage is that the journal would only be updated by the normal flush to disk fetch operations. If you had a power failure, as an example, you would loose whatever data had not been flushed to disk since the last normal, on demand cycle. With ordered mode, which is the default, you would at most loose the last five seconds. It is a trade off that I would gladly do on a laptop. After all, how often do you have a power failure on a laptop.
If you are interested, the instructions for changing the mode are in one of my earlier posts.
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