strange perlbal problem

[Eric Chang]

I've successed install perlbal and mogilefs.
Our front end is  ZXTM (http://www.zeus.com)
then ->  2 perlbal nodes,
then ->2 web ap(mod_php)+mogilefs tracker nodes,
and 2 mogstored nodes as storage.
our web ap pass reproxy header back to perlbal for fetching real file
from mogstored.
All works fine, but we have some slow response problem,
Sometimes, browser just loading and hang , client should wait about 10
or more seconds..
after that the page display correctly.
So..
1. I test the web ap node, connect directly, no hang and slow problem.
2.I change ZXTM setting bypass perlbal node and go to web ap node
directly, -> no hang and slow problem,too.

I've no idea how to solve this..

My setup:
Gentoo Linux 2.6
perl 5.8.6
Dual  Opteron
2g
Perlabl 1.39
Danga-Socket 1.48
Mogilefs (cvs)

---------perlbal.conf--------
LOAD vhosts
xs enable headers
SERVER aio_mode = linux
SERVER aio_threads = 36
# apache pools
CREATE POOL apaches
    POOL apaches ADD 10.0.0.31:80
    POOL apaches ADD 10.0.0.32:80

# *.blog.foo.com
CREATE SERVICE blog
>---SET listen          = 0.0.0.0:81
>---SET role            = reverse_proxy
>---SET pool            = apaches
>---SET persist_client  = on
>---SET persist_backend = on
>---SET verify_backend  = on
    SET always_trusted  = on
    SET enable_reproxy  = on
    SET buffer_uploads  = on
    SET buffer_backend_connect = 128k
ENABLE blog

CREATE SERVICE maintains
    SET listen      = 0.0.0.0:82
    SET role        = web_server
    SET docroot     = /home/system
    SET dirindexing = 1
    SET persist_client = on
ENABLE maintains
# *.*
CREATE SERVICE vhost-
  SET listen         = 0.0.0.0:80
  SET role           = selector
  SET plugins        = vhosts
  SET persist_client = on
  VHOST *.blog.foo.com = blog
  VHOST moblog.foo.com = blog
ENABLE vhost

# always good to keep an internal management port open:
CREATE SERVICE mgmt
  SET role   = management
  SET listen = 127.0.0.1:60000
ENABLE mgmt