1 <html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>Chapter 43. Samba Performance Tuning</title><link rel="stylesheet" href="samba.css" type="text/css"><meta name="generator" content="DocBook XSL Stylesheets V1.68.1"><link rel="start" href="index.html" title="The Official Samba-3 HOWTO and Reference Guide"><link rel="up" href="Appendix.html" title="Part VI. Reference Section"><link rel="prev" href="Other-Clients.html" title="Chapter 42. Samba and Other CIFS Clients"><link rel="next" href="ch-ldap-tls.html" title="Chapter 44. LDAP and Transport Layer Security"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 43. Samba Performance Tuning</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="Other-Clients.html">Prev</a> </td><th width="60%" align="center">Part VI. Reference Section</th><td width="20%" align="right"> <a accesskey="n" href="ch-ldap-tls.html">Next</a></td></tr></table><hr></div><div class="chapter" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="speed"></a>Chapter 43. Samba Performance Tuning</h2></div><div><div class="author"><h3 class="author"><span class="firstname">Paul</span> <span class="surname">Cochrane</span></h3><div class="affiliation"><span class="orgname">Dundee Limb Fitting Centre<br></span><div class="address"><p><code class="email"><<a href="mailto:paulc@dth.scot.nhs.uk">paulc@dth.scot.nhs.uk</a>></code></p></div></div></div></div><div><div class="author"><h3 class="author"><span class="firstname">Jelmer</span> <span class="othername">R.</span> <span class="surname">Vernooij</span></h3><div class="affiliation"><span class="orgname">The Samba Team<br></span><div class="address"><p><code class="email"><<a href="mailto:jelmer@samba.org">jelmer@samba.org</a>></code></p></div></div></div></div><div><div class="author"><h3 class="author"><span class="firstname">John</span> <span class="othername">H.</span> <span class="surname">Terpstra</span></h3><div class="affiliation"><span class="orgname">Samba Team<br></span><div class="address"><p><code class="email"><<a href="mailto:jht@samba.org">jht@samba.org</a>></code></p></div></div></div></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="sect1"><a href="speed.html#id2656385">Comparisons</a></span></dt><dt><span class="sect1"><a href="speed.html#id2656423">Socket Options</a></span></dt><dt><span class="sect1"><a href="speed.html#id2656510">Read Size</a></span></dt><dt><span class="sect1"><a href="speed.html#id2656549">Max Xmit</a></span></dt><dt><span class="sect1"><a href="speed.html#id2656592">Log Level</a></span></dt><dt><span class="sect1"><a href="speed.html#id2656612">Read Raw</a></span></dt><dt><span class="sect1"><a href="speed.html#id2656662">Write Raw</a></span></dt><dt><span class="sect1"><a href="speed.html#id2656702">Slow Logins</a></span></dt><dt><span class="sect1"><a href="speed.html#id2656721">Client Tuning</a></span></dt><dt><span class="sect1"><a href="speed.html#id2656742">Samba Performance Problem Due to Changing Linux Kernel</a></span></dt><dt><span class="sect1"><a href="speed.html#id2656834">Corrupt tdb Files</a></span></dt><dt><span class="sect1"><a href="speed.html#id2656930">Samba Performance is Very Slow</a></span></dt></dl></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2656385"></a>Comparisons</h2></div></div></div><p>
2 The Samba server uses TCP to talk to the client, so if you are
3 trying to see if it performs well, you should really compare it to
4 programs that use the same protocol. The most readily available
5 programs for file transfer that use TCP are ftp or another TCP-based
8 If you want to test against something like an NT or Windows for Workgroups server, then
9 you will have to disable all but TCP on either the client or
10 server. Otherwise, you may well be using a totally different protocol
11 (such as NetBEUI) and comparisons may not be valid.
13 Generally, you should find that Samba performs similarly to ftp at raw
14 transfer speed. It should perform quite a bit faster than NFS,
15 although this depends on your system.
17 Several people have done comparisons between Samba and Novell, NFS, or
18 Windows NT. In some cases Samba performed the best, in others the worst. I
19 suspect the biggest factor is not Samba versus some other system, but the
20 hardware and drivers used on the various systems. Given similar
21 hardware, Samba should certainly be competitive in speed with other
23 </p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2656423"></a>Socket Options</h2></div></div></div><p>
24 There are a number of socket options that can greatly affect the
25 performance of a TCP-based server like Samba.
27 The socket options that Samba uses are settable both on the command
28 line with the <code class="option">-O</code> option and in the <code class="filename">smb.conf</code> file.
30 The <a class="indexterm" name="id2656451"></a>socket options section of the <code class="filename">smb.conf</code> manual page describes how
31 to set these and gives recommendations.
33 Getting the socket options correct can make a big difference to your
34 performance, but getting them wrong can degrade it by just as
35 much. The correct settings are very dependent on your local network.
37 The socket option TCP_NODELAY is the one that seems to make the biggest single difference
38 for most networks. Many people report that adding
39 <a class="indexterm" name="id2656478"></a>socket options = TCP_NODELAY
40 doubles the read performance of a Samba drive. The best explanation I have seen for
41 this is that the Microsoft TCP/IP stack is slow in sending TCP ACKs.
43 There have been reports that setting <em class="parameter"><code>socket options = SO_RCVBUF=8192</code></em> in smb.conf
44 can seriously degrade Samba performance on the loopback adaptor (IP Address 127.0.0.1). It is strongly
45 recommended that before specifying any settings for <em class="parameter"><code>socket options</code></em>, the effect
46 first be quantitatively measured on the server being configured.
47 </p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2656510"></a>Read Size</h2></div></div></div><p>
48 The option <a class="indexterm" name="id2656518"></a>read size affects the overlap of disk
49 reads/writes with network reads/writes. If the amount of data being
50 transferred in several of the SMB commands (currently SMBwrite, SMBwriteX, and
51 SMBreadbraw) is larger than this value, then the server begins writing
52 the data before it has received the whole packet from the network, or
53 in the case of SMBreadbraw, it begins writing to the network before
54 all the data has been read from disk.
56 This overlapping works best when the speeds of disk and network access
57 are similar, having little effect when the speed of one is much
58 greater than the other.
60 The default value is 16384, but little experimentation has been
61 done as yet to determine the optimal value, and it is likely that the best
62 value will vary greatly between systems anyway. A value over 65536 is
63 pointless and will cause you to allocate memory unnecessarily.
64 </p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2656549"></a>Max Xmit</h2></div></div></div><p>
65 At startup the client and server negotiate a <em class="parameter"><code>maximum transmit</code></em> size,
66 which limits the size of nearly all SMB commands. You can set the
67 maximum size that Samba will negotiate using the <a class="indexterm" name="id2656565"></a>max xmit option
68 in <code class="filename">smb.conf</code>. Note that this is the maximum size of SMB requests that
69 Samba will accept, but not the maximum size that the client will accept.
70 The client maximum receive size is sent to Samba by the client, and Samba
73 It defaults to 65536 bytes (the maximum), but it is possible that some
74 clients may perform better with a smaller transmit unit. Trying values
75 of less than 2048 is likely to cause severe problems.
76 In most cases the default is the best option.
77 </p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2656592"></a>Log Level</h2></div></div></div><p>
78 If you set the log level (also known as <a class="indexterm" name="id2656600"></a>debug level) higher than 2,
79 then you may suffer a large drop in performance. This is because the
80 server flushes the log file after each operation, which can be quite
82 </p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2656612"></a>Read Raw</h2></div></div></div><p>
83 The <a class="indexterm" name="id2656620"></a>read raw operation is designed to be an optimized, low-latency
84 file read operation. A server may choose to not support it,
85 however, and Samba makes support for <a class="indexterm" name="id2656630"></a>read raw optional, with it
86 being enabled by default.
88 In some cases clients do not handle <a class="indexterm" name="id2656642"></a>read raw very well and actually
89 get lower performance using it than they get using the conventional
90 read operations, so you might like to try <a class="indexterm" name="id2656651"></a>read raw = no and see what happens on your
91 network. It might lower, raise, or not affect your performance. Only
92 testing can really tell.
93 </p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2656662"></a>Write Raw</h2></div></div></div><p>
94 The <a class="indexterm" name="id2656670"></a>write raw operation is designed to be an optimized, low-latency
95 file write operation. A server may choose to not support it, however, and Samba makes support for
96 <a class="indexterm" name="id2656680"></a>write raw optional, with it being enabled by default.
98 Some machines may find <a class="indexterm" name="id2656691"></a>write raw slower than normal write, in which
99 case you may wish to change this option.
100 </p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2656702"></a>Slow Logins</h2></div></div></div><p>
101 Slow logins are almost always due to the password checking time. Using
102 the lowest practical <a class="indexterm" name="id2656711"></a>password level will improve things.
103 </p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2656721"></a>Client Tuning</h2></div></div></div><p>
104 Often a speed problem can be traced to the client. The client (for
105 example Windows for Workgroups) can often be tuned for better TCP
106 performance. Check the sections on the various clients in
107 <a href="Other-Clients.html" title="Chapter 42. Samba and Other CIFS Clients">Samba and Other CIFS Clients</a>.
108 </p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2656742"></a>Samba Performance Problem Due to Changing Linux Kernel</h2></div></div></div><p>
109 A user wrote the following to the mailing list:
110 </p><div class="blockquote"><blockquote class="blockquote"><p>
111 <a class="indexterm" name="id2656757"></a>
112 <a class="indexterm" name="id2656764"></a>
113 I am running Gentoo on my server and Samba 2.2.8a. Recently I changed kernel versions from
114 <code class="filename">linux-2.4.19-gentoo-r10</code> to <code class="filename">linux-2.4.20-wolk4.0s</code>. Now I have a
115 performance issue with Samba. Many of you will probably say, “<span class="quote">Move to vanilla sources!</span>” Well, I
116 tried that and it didn't work. I have a 100MB LAN and two computers (Linux and Windows 2000). The Linux server
117 shares directories with DivX files, the client (Windows 2000) plays them via LAN. Before, when I was running
118 the 2.4.19 kernel, everything was fine, but now movies freeze and stop. I tried moving files between the
119 server and Windows, and it is terribly slow.
120 </p></blockquote></div><p>
121 The answer he was given is:
122 </p><div class="blockquote"><blockquote class="blockquote"><p>
123 <a class="indexterm" name="id2656806"></a>
124 <a class="indexterm" name="id2656813"></a>
125 <a class="indexterm" name="id2656820"></a>
126 Grab the mii-tool and check the duplex settings on the NIC. My guess is that it is a link layer issue, not an
127 application layer problem. Also run ifconfig and verify that the framing error, collisions, and so on, look
129 </p></blockquote></div></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2656834"></a>Corrupt tdb Files</h2></div></div></div><p>
130 <a class="indexterm" name="id2656842"></a>
131 <a class="indexterm" name="id2656849"></a>
132 <a class="indexterm" name="id2656856"></a>
133 Our Samba PDC server has been hosting three TB of data to our 500+ users [Windows NT/XP] for the last three
134 years using Samba without a problem. Today all shares went very slow. Also, the main smbd kept spawning new
135 processes, so we had 1600+ running SMDB's (normally we average 250). It crashed the SUN E3500 cluster twice.
136 After a lot of searching, I decided to <span><strong class="command">rm /var/locks/*.tdb</strong></span>. Happy again.
138 <span class="emphasis"><em>Question:</em></span> Is there any method of keeping the *.tdb files in top condition, or
139 how can I detect early corruption?
141 <a class="indexterm" name="id2656887"></a>
142 <a class="indexterm" name="id2656894"></a>
143 <span class="emphasis"><em>Answer:</em></span> Yes, run <span><strong class="command">tdbbackup</strong></span> each time after stopping nmbd and before starting nmbd.
145 <span class="emphasis"><em>Question:</em></span> What I also would like to mention is that the service latency seems
146 a lot lower than before the locks cleanup. Any ideas on keeping it top notch?
148 <span class="emphasis"><em>Answer:</em></span> Yes. Same answer as for previous question!
149 </p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2656930"></a>Samba Performance is Very Slow</h2></div></div></div><p>
150 <a class="indexterm" name="id2656938"></a>
151 A site reported experiencing very baffling symptoms with MYOB Premier opening and
152 accessing its data files. Some operations on the file would take between 40 and
155 <a class="indexterm" name="id2656951"></a>
156 <a class="indexterm" name="id2656958"></a>
157 It turned out that the printer monitor program running on the Windows
158 clients was causing the problems. From the logs, we saw activity coming
159 through with pauses of about 1 second.
161 <a class="indexterm" name="id2656971"></a>
162 <a class="indexterm" name="id2656978"></a>
163 Stopping the monitor software resulted in the networks access at normal
164 (quick) speed. Restarting the program caused the speed to slow down
165 again. The printer was a Canon LBP-810 and the relevant task was
166 something like CAPON (not sure on spelling). The monitor software
167 displayed a "printing now" dialog on the client during printing.
169 We discovered this by starting with a clean install of Windows and
170 trying the application at every step of the installation of other software
171 process (we had to do this many times).
173 Moral of the story: Check everything (other software included)!
174 </p></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="Other-Clients.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="Appendix.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="ch-ldap-tls.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 42. Samba and Other CIFS Clients </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 44. LDAP and Transport Layer Security</td></tr></table></div></body></html>
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