Incorporate README.fsync into main documentation body

doc/README.fsync

-Fsync() patch (backend -F option)
-=================================
-
-Normally, the Postgres'95 backend makes sure that updates are actually
-committed to disk by calling the standard function fsync() in
-several places. Fsync() should guarantee that every modification to
-a certain file is actually written to disk and will not hang around
-in write caches anymore. This increases the chance that a database
-will still be usable after a system crash by a large amount.
-
-However, this operation severely slows down Postgres'95, because at all
-those points it has to wait for the OS to flush the buffers. Especially
-in one-shot operations, like creating a new database or loading lots
-of data, you'll have a clear restart point if something goes wrong. That's
-where the -F option kicks in: it simply disables the calls to fsync(). 
-
-Without fsync(), the OS is allowed to do its best in buffering, sorting
-and delaying writes, so this can be a _very_ big perfomance increase. However,
-if the system crashes, large parts of the latest transactions will still hang
-around in memory without having been committed to disk - lossage of data
-is therefore almost certain to occur.
-
-So it's a tradeoff between data integrity and speed. When initializing a
-database, I'd use it - if the machine crashes, you simply remove the files
-created and redo the operation. The same goes for bulk-loading data: on
-a crash, you remove the database and restore the backup you made before
-starting the bulk-load (you always make backups before bulk-loading,
-don't you?).
-
-Whether you want to use it in production, is up to you. If you trust your
-operating system, your utility company, and your hardware, you might enable
-it; however, keep in mind that you're running in an unsecure mode and that
-performance gains will very much depend on access patterns (because it won't
-help on reading data). I'd recommend against it.

doc/src/sgml/runtime.sgml

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 <Chapter Id="runtime">
@@ -846,11 +846,39 @@ env PGOPTIONS='--geqo=off' psql
       <term>FSYNC (<type>boolean</type>)</term>
       <listitem>
        <para>
-        When this is on (default), an <function>fsync()</function>
-        call is done after each transaction. Turning this off
-        increases performance but an operating system crash or power
-        outage might cause data corruption. (Note that a crash of
-        <productname>Postgres</productname> itself is not affected.)
+        If this is option is on, the <productname>Postgres</> backend
+        will use the <function>fsync()</> system call in several
+        places to make sure that updates are physically written to
+        disk and will not hang around in the write caches. This
+        increases the chance that a database installation will still
+        be usable after a operating system or hardware crashes by a
+        large amount. (Crashes of the database server itself do
+        <emphasis>not</> affect this consideration.)
+       </para>
+
+       <para>
+        However, this operation severely slows down
+        <productname>Postgres</>, because at all those points it has
+        to block and wait for the operating system to flush the
+        buffers. Without <function>fsync</>, the operating system is
+        allowed to do its best in buffering, sorting, and delaying
+        writes, so this can be a <emphasis>very</> big perfomance
+        increase. However, if the system crashes, parts of the data of
+        a transaction that has already been committed -- according to
+        the information on disk -- will still hang around in memory.
+        Inconsistent data (i.e., data corruption) is therefore likely
+        to occur.
+       </para>
+
+       <para>
+        This option is the subject of an eternal debate in the
+        <productname>Postgres</> user and developer communities. Some
+        always leave it off, some turn it off only for bulk loads,
+        where there is a clear restart point if something goes wrong,
+        some leave it on just to be on the safe side. Because it is
+        the safe side, on is also the default. If you trust your
+        operating system, your utility company, and your hardware, you
+        might want to disable it.
        </para>
       </listitem>
      </varlistentry>