Some advanced database features, are they present in PostgreSQL

Hi,

I have been using PostgreSQL a bit and I have been surprised by the good
quality, the features, and now the Addison-Wesley book which is excellent.
However, I have some questions about the implementation of a few
additional features.

I suppose that PostgreSQL hasn't any ability to do the following yet:

   - log all transactions to a special log file, that can be used for
     backup purposes: ie you dump the database every day, but you keep
     the transaction log on a separate disk. Should the database disk
     crash, you won't have any data loss if you restore the backup and
     replay the transaction log.

   - hard transactions: cutting the power to a PostgreSQL server
     may cause data loss and/or data corruption. Some databases use
     sophisticated techniques to ensure serialization of operation
     through journaling, redoing some of the transactions at
     bootup time if required.

   - the ability to synchronize two database servers, with only the
     changes being exchanged, live. Or the ability to have many
     servers in a load-balancing or data scattering pool.

   - ability to have databases bigger than the host's maximum file size

if this is true, can someone tell me why it hasn't been implemented yet
(there might be very good reasons), if it will be, and if the task seems
complicated.

thank you for your time.