[Samba] 10-fold speed drop while transferring large files from Windows to Samba server

[Dmitri Pechkin]

Hi All,

I have a Linux box (P3-800MHz/196MB RAM/10GB+320GB) running Samba
3.0.22 server and a Windows XP (P3-800MHz/512MB RAM/200GB) client.

The transfer speed (both ways) is about 5-7 MB/s when file is smaller
than 700MB. For larger files there is a difference: when the Win client
writes a file on the small Linux disk (10GB) the speed is as above. But
when I copy, let's say, a 1.5GB file from Win to the 320GB disk on
Linux the speed is 7 MB/s for the first 50% of the trasfer and then it
drops down to 600 KB/s. Here is an vmstat log of the session:

procs -----------memory---------- ---swap-- -----io---- --system--
----cpu----
  r  b   swpd   free   buff  cache   si   so    bi    bo   in    cs us
sy id wa
  0  0  85552  17676   1760  78844    0    0     4  3291 5583  5817  4
22 69  5
  0  1  85632   1184   1152  95876    0    8     2  6788 8327  9078  6
36 16 42
  0  1  85632    524    624  97168    0    0     0  6934 8682  9466  5
38  6 52
  0  1  85632    484    552  97156    0    0     4  7190 8591  9441  5
38  6 51
  0  5  85632    904    752  95776    8    0    44  7126 8850  9739  5
39  5 51
  0  2  85632   1228   1308  95156    3    0   262  7230 8932  9882 15
41  6 38
  0  1  85632    420    988  96612    0    0    12  7156 8762  9665  5
39  6 50
  1  2  85632    532    744  96760    0    0    10  7251 8807  9828  5
39  6 50
  1  1  85632    520    724  96800    0    0     8  7534 9110 10189  5
40  6 50
  0  1  85632   1012    840  96172    0    0     7  7332 8947 10018  5
40  7 49
  0  2  85632   1204   1520  94368    0    0    72  5060 7633  8387  5
33  7 55
  1  2  85632   1812   7048  82392    0    0   552     2 1148   470  2
2  0 96
  1  0  85632   1260  10168  76360    0    0   315  1888 1395   612  2
46  1 51
  1  0  85632   1040  10184  76676    2    0     3   610 1597   803  3
94  2  2
  2  0  85632   1008  10200  76708    1    0     2   606 1598   809  2
94  2  1
  1  0  85632   1228  10212  76484    0    0     0   612 1599   815  3
93  3  1
  1  1  85632   1456  10216  76356    0    0     0   606 1602   807  2
94  2  2
  1  1  85632   1232  10212  76588    0    0     1   592 1600   810  2
95  2  1
  2  1  85632   1248  10188  76596    0    0     0   595 1600   838  3
93  2  2
  1  1  85632   1312  10776  75916    0    0   564   807 1666   955  3
93  1  3
  1  1  85632   1428  10852  75628    0    0    52   594 1614   838  3
94  2  1
  2  1  85632   1520  10864  75496    0    0     0   596 1601   814  2
94  2  1
  1  0  85632   1596  10808  75512    0    0     1   597 1595   830  3
94  2  1
  1  1  85632   1016  10780  76076    0    0     0   600 1568   650  2
95  2  1

>From the above report, the CPU use jumps from 35-40% to 95% and 'top'
shows that it attributes entirely to the 'smbd' process.

Here is my smb.conf:

================== smb.conf ======================
[root at pioneer samba]# /opt/samba-3.0.22/bin/testparm
</etc/samba/smb.conf
Load smb config files from /opt/samba-3.0.22/lib/smb.conf
Processing section "[homes]"
Processing section "[printers]"
Processing section "[samba]"
Loaded services file OK.
WARNING: passdb expand explicit = yes is deprecated
Server role: ROLE_STANDALONE
Press enter to see a dump of your service definitions
[global]
         server string = Samba Server
         password server = None
         username map = /etc/samba/smbusers
         log file = /var/log/samba/%m.log
         max log size = 50
         socket options = TCP_NODELAY SO_RCVBUF=8192 SO_SNDBUF=8192
         printcap name = /etc/printcap
         dns proxy = No
         remote announce = 192.168.1.255
         idmap uid = 16777216-33554431
         idmap gid = 16777216-33554431
         hosts allow = 192.168.1.
         cups options = raw
[homes]
         comment = Home Directories
         read only = No
         browseable = No
[printers]
         comment = All Printers
         path = /var/spool/samba
         printable = Yes
         browseable = No
[samba]
         path = /home/samba
         read only = No
================== smb.conf ======================

Googling for similar problems, I found some people reporting such
behaivor but I was not able to find any suggestions how to fix the
issue. I am thinking to add some more memory but not sure whether it
would help.

Important note, that in my case this problem happens ONLY with the
large 320GB hard drive, not with the small one.

I very appreciate any suggestions to resolve this problem.

Regards,
Dmitri