The dangers of "-F"

I've mentioned in the past that the fsynch following
every select, even when no data is modified, is a
killer for high-volume web sites that make many short,
read-only hits on the database (for page customization,
for example).

I know that fixing this is on the "to do" list. I've
known of the "-F" switch for some time, but the recent
round of posts triggered by someone observing lots of
disk thrashing and the fact that I'm getting close to
going online with my first round of web services based
on Postgres motivated me to give it a try.

It's very, very nice to have the disk silent when
hitting it with a bunch of simultaneous "selects"
from different http connections. It really increases
throughput, and is much, much kinder to the disk.
The difference for lots of short hits is very high.

So obviously I'm really looking forward to the day
when a read-only select doesn't trigger a write to
pg_log (which apparently is the problem?) and an
"fsynch the world" operation.

In the interim, just how dangerous is it to run with
"-F"?

Am I risking corruption of the db and a total rebuild,
or will I just lose transactions but be left with a
consistent database if the machine goes down?

- Don Baccus, Portland OR <dhogaza(at)pacifier(dot)com>
Nature photos, on-line guides, and other goodies at
http://donb.photo.net