Stability and safety. Production environments are going to be more comfortable with a small incremental change to their existing FS than they are in switching and potentially being bitten by one of the many major changes in ext4.
Posted Apr 16, 2009 19:35 UTC (Thu) by jordanb (guest, #45668)
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I think the idea is that ext3 is being made less reliable so that it will no longer be more reliable than ext4, to try to remove that argument against "upgrading."