[Samba] poor performances at the end of the day

[thomas constans]

hello list

here is the setup:

a domain controller with ldap backend.
os is debian testing with custom 2.6.9 kernel
samba version 3.0.10-1
openldap version 2.1.30-3
local profiles only
clients are mainly nt4 sp6, some win xp pro
approximately 30 win users + 1 or 2 diskless linux station for testing
purpose (ltsp ).

16 directories shared by server, including homedirs, with acl support
( 20GO og data )

here is the setup:

users experience network slowdown at the end of the work day ( slow
transfer, slow win epxlorer operations ... ).

cpu and net load on server side is insignifiant ( it is an oversized
dual p4 w/ giga ethernet and 4 Gig of ram ).

i dont even know if the problem is related to samba, i am just expecting
some idea as to where/what to look at.

relevant portion of smb.conf:
   netbios name = server
   server string = controleur du domaine
   workgroup = gr_travail
   domain logons = true
   domain master = true
   os level = 35
   prefered master = yes
   encrypt passwords = true

   socket options = TCP_NODELAY SO_RCVBUF=8192 SO_SNDBUF=8192
   interfaces = 127.0.0.1 192.168.1.2

   passdb backend = ldapsam
   ldap ssl = No
   ldap admin dn = cn=admin,dc=gr_travail
   ldap suffix = dc=rgr_travail
   ldap machine suffix = ou=machines
   ldap user suffix = ou=utilisateurs
   ldap group suffix = ou=groupes

   log file = /var/log/samba/samba.log
   log level = 0
   load printers = yes
   printing = cups
   printcap name = cups
   dos charset = cp850
   unix charset = iso8859-1


relevant portions of slapd.conf:
backend        bdb
database       bdb
checkpoint     1 5
cachesize      100000
idletimeout 20
index   objectClass,uid,uidNumber,gidNumber,memberUid   eq
index   cn,mail,surname,givenname                       eq,subinitial


thanks for your patience and your aswers

-- 
Thomas Constans
http://www.opendoor.fr
04 78 68 17 34