Postgresql 9.3 tuning advice

Hello all,

Iam running a postgresql 9.0.13 master/slave instance in a write heavy
workload.

The hardware is a Dell 720, E5530 - 8 core, 128GB RAM. The database (around
250g with indexes/bloat etc) is sitting on flashcache device with 2 fusion-
io PCIe MLC SSDs as frontend and a MD3200 based RAID10 (14*1TB SATA disks)
as backend. OS is centos 6.2 with kernel 2.6.32-431.20.3.el6.x86_64.

Currently, the performance related configuration is mostly default i,e
shared_buffers,
effective_cache_size. The only directive that seems different is
checkpoint_segments = 96

Iam moving to postgresql 9.3 shortly and planning to tune the above
directives as below..

effective_cache_size = 100GB # free+buffers is pretty consistent around 110
to 120GB and pg_oscache_total is around 80GB
checkpoint_segments = 32 # 96 seems to long and all flushes seem to be only
due to checkpoint_timeout with the older value

Additionally iam turning off THB defrag on the OS as suggested by some
posts on the
lists. Though, My initial pgbench testing doesn't seem to indicate any
issues with THB defrag turned on/off.

Iam not sure about shared_buffers and wal_buffers for this HW/OS & DB
combination - iam inclined to leave
them to defaults. But based on this article
(http://rhaas.blogspot.in/2012/03/tuning-sharedbuffers-and-walbuffers.html)
it looks there will be some advantages in tuning it

What would be a good value (to start with atleast) for shared_buffers and
wal_buffers ?

Please let me know if additional information will help.

TIA
dushy