Planning hot/live backups?

The owners of the animal hospital where I work at want to consider live/hot
backups through out the day so we're less likely to lose a whole
day of transaction.  We use Postgresql 8.0.15. We do 3AM
backups, using pg_dumpall, to a file when there is very little activity.

The hospital enjoys the overall performance of the veterinary
application running
on Postgresql. I know doing a mid-day backup when up to 60 computers
(consistently
35-40) are access client/patient information, it will cause some
frustration. I understand
there needs to be balance of performance and backup of current records.

While I know that not all situations are the same, I am hoping there
is a performance
latency that others have experienced when doing backups during the day and/or
planning for cluster (or other types of redundancy).

My animal hospital operates 24x7 and is in the south part of the San
Francisco Bay area. Outside
of sharing your experiences/input with me, I would not mind if you/your company
do this type of consulting offline.

Thank you.

Steve