[Samba] Slow samba transfer

[Roberto su tiscali]

Thats the diagnosis:
transfering the same file via smb, scp and ftp I got big speed 
differences.
SMB:
file : 1Gb, transfer rate 15-35 kb/s
SCP:
file : 1Gb, transfer rate 360-780 kb/s
FTP:
file : 1Gb, transfer rate 360-780 kb/s


Why is via smb so slow?
Attachment is my own smb:conf, the same that's on air.


[global]
workgroup = NO1KNOWS
netbios name = PBT
   server string = Samba %v, File server
;   wins support = no
;   wins server = w.x.y.z
   dns proxy = no
   os level = 64
;   name resolve order = lmhosts host wins bcast
   log file = /var/log/samba/log.%m
   max log size = 50
;   syslog only = no
   syslog = 0
   panic action = /usr/share/samba/panic-action %d

####### Authentication #######
   security = user
   encrypt passwords = yes
passdb backend = tdbsam guest
   obey pam restrictions = yes
;   guest account = nobody
   invalid users = root
unix password sync = yes
passwd program = /usr/bin/passwd %u
passwd chat = *Enter\snew\sUNIX\spassword:* %n\n 
*Retype\snew\sUNIX\spassword:* %n\n .
;   pam password change = no
  socket options = TCP_NODELAY IPTOS_LOWDELAY SO_SNDBUF=8192 
SORCVBUF=8192
local master = yes
   domain master =yes

#Other stuff ;-))
domain logons = yes
hosts allow = 127.0.0.1 192.168.1.0/255.255.255.0 
192.168.2.0/255.255.255.0 192.168.3.0/255.255.255.0
logon home = \\%L\%U\.profile
logon path = \\%L\profile\%U
logon drive = H:
logon script = netlogon.bat

[homes]
   comment = Home Directories
   browseable = no
   writable = yes
   create mask = 0700
   directory mask = 0700

[profile]
path = /home/samba/profile
writable = yes
browsable = no
create mask = 600
directory mask = 700

# Un-comment the following and create the netlogon directory for Domain 
Logons
# (you need to configure Samba to act as a domain controller too.)

[netlogon]
   comment = Network Logon Service
   path = /home/samba/netlogon
   read only = yes
   write list = @admin
   guest ok = no
   writable = no
   share modes = no
   browsable = no
[Tutto]
   path = /mnt/
   writable = yes
   directory mask = 0754
   browseable = yes
#   read only = yes
   guest ok = yes


[Condivisa]
   path = /shared/
   writable = yes
   directory mask = 0774
   browseable = yes
#   read only = yes
   guest ok = yes

Help a honest worker!
thanx to all