Is PostgreSQL supported on RHEL6?

Hello,

I have some software products which support RHEL5 for x86 and x86_64. Each
of them uses PostgreSQL 8.3.12 as a data repository. They all embed the same
PostgreSQL binaries.

Now I'm trying to support both RHEL5 and RHEL6 with minimal effort (but with
safety). If possible, I want to continue to use PostgreSQL 8.3.12 built on
RHEL5 for a while. Then, I'd like to ask some questions:

Q1: Is it safe to use PostgreSQL 8.3.12 on RHEL6? If it is not safe, what
kind of problems might happen?
I could build 8.3.12 successfully with 167 compilation warnings that report
"variable not used" and "uninitialized variable is used" etc. Even if I
could run PostgreSQL, I'm not sure that it is safe. I wonder if running the
regression tests reveals problems.

I searched the PostgreSQL mailing lists with "RHEL6" and found the
discussion regarding wal_sync_method and O_DSYNC/O_SYNC. The following fix
in 8.3.13 makes me wonder if I should update with 8.3.14 which is the latest
version of 8.3 series. Is it safe to use 8.3.12 on RHEL6 by setting
wal_sync_method to fdatasync?

----------------------------------------
8.3.13 release note
http://www.postgresql.org/docs/8.3/static/release-8-3-13.html
...
Force the default wal_sync_method to be fdatasync on Linux (Tom Lane, Marti
Raudsepp)
The default on Linux has actually been fdatasync for many years, but recent
kernel changes caused PostgreSQL to choose open_datasync instead. This
choice did not result in any performance improvement, and caused outright
failures on certain filesystems, notably ext4 with the data=journal mount
option.
----------------------------------------

Q2: If 8.3.12 is not safe on RHEL6, is 8.3.14 safe? Do I need to use 9.0.3
on RHEL6?
I want to avoid upgrading to a newer major version (9.0) because my software
do not need new features in 9.0 yet.

Q3: Doesn't PostgreSQL's performance degrade on RHEL6?
As stated above, by searching the PostgreSQL mailing lists and other web
sites, I knew that O_SYNC was implemented in Linux kernel and fsync() got
slower (on ext4 than on ext3?). Do these mean that running PostgreSQL on
RHEL6 is not appropriate yet?

Regards
MauMau