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+<html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>Chapter 39. Samba Performance Tuning</title><link rel="stylesheet" href="samba.css" type="text/css"><meta name="generator" content="DocBook XSL Stylesheets V1.60.1"><link rel="home" href="samba-doc.html" title="SAMBA Project Documentation"><link rel="up" href="Appendixes.html" title="Part VI. Appendixes"><link rel="previous" href="Other-Clients.html" title="Chapter 38. Samba and other CIFS clients"><link rel="next" href="DNSDHCP.html" title="Chapter 40. DNS and DHCP Configuration Guide"></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 39. 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. Appendixes</th><td width="20%" align="right"> <a accesskey="n" href="DNSDHCP.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 39. 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><tt class="email">&lt;<a href="mailto:paulc@dth.scot.nhs.uk">paulc@dth.scot.nhs.uk</a>&gt;</tt></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><tt class="email">&lt;<a href="mailto:jelmer@samba.org">jelmer@samba.org</a>&gt;</tt></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><tt class="email">&lt;<a href="mailto:jht@samba.org">jht@samba.org</a>&gt;</tt></p></div></div></div></div></div><div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><a href="speed.html#id2964209">Comparisons</a></dt><dt><a href="speed.html#id2964253">Socket options</a></dt><dt><a href="speed.html#id2964343">Read size</a></dt><dt><a href="speed.html#id2964393">Max xmit</a></dt><dt><a href="speed.html#id2964453">Log level</a></dt><dt><a href="speed.html#id2964483">Read raw</a></dt><dt><a href="speed.html#id2964567">Write raw</a></dt><dt><a href="speed.html#id2964630">Slow Logins</a></dt><dt><a href="speed.html#id2964659">Client tuning</a></dt><dt><a href="speed.html#id2964684">Samba performance problem due changing kernel</a></dt><dt><a href="speed.html#id2964716">Corrupt tdb Files</a></dt></dl></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2964209"></a>Comparisons</h2></div></div><div></div></div><p>
+The Samba server uses TCP to talk to the client. Thus if you are
+trying to see if it performs well you should really compare it to
+programs that use the same protocol. The most readily available
+programs for file transfer that use TCP are ftp or another TCP based
+SMB server.
+</p><p>
+If you want to test against something like a NT or WfWg server then
+you will have to disable all but TCP on either the client or
+server. Otherwise you may well be using a totally different protocol
+(such as NetBEUI) and comparisons may not be valid.
+</p><p>
+Generally you should find that Samba performs similarly to ftp at raw
+transfer speed. It should perform quite a bit faster than NFS,
+although this very much depends on your system.
+</p><p>
+Several people have done comparisons between Samba and Novell, NFS or
+WinNT. In some cases Samba performed the best, in others the worst. I
+suspect the biggest factor is not Samba vs some other system but the
+hardware and drivers used on the various systems. Given similar
+hardware Samba should certainly be competitive in speed with other
+systems.
+</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2964253"></a>Socket options</h2></div></div><div></div></div><p>
+There are a number of socket options that can greatly affect the
+performance of a TCP based server like Samba.
+</p><p>
+The socket options that Samba uses are settable both on the command
+line with the <tt class="option">-O</tt> option, or in the <tt class="filename">smb.conf</tt> file.
+</p><p>
+The <a class="indexterm" name="id2964287"></a><i class="parameter"><tt>socket options</tt></i> section of the <tt class="filename">smb.conf</tt> manual page describes how
+to set these and gives recommendations.
+</p><p>
+Getting the socket options right can make a big difference to your
+performance, but getting them wrong can degrade it by just as
+much. The correct settings are very dependent on your local network.
+</p><p>
+The socket option TCP_NODELAY is the one that seems to make the
+biggest single difference for most networks. Many people report that
+adding <a class="indexterm" name="id2964323"></a><i class="parameter"><tt>socket options</tt></i> = TCP_NODELAY doubles the read 
+performance of a Samba drive. The best explanation I have seen for this is
+that the Microsoft TCP/IP stack is slow in sending tcp ACKs.
+</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2964343"></a>Read size</h2></div></div><div></div></div><p>
+The option <a class="indexterm" name="id2964353"></a><i class="parameter"><tt>read size</tt></i> affects the overlap of disk
+reads/writes with network reads/writes. If the amount of data being
+transferred in several of the SMB commands (currently SMBwrite, SMBwriteX and
+SMBreadbraw) is larger than this value then the server begins writing
+the data before it has received the whole packet from the network, or
+in the case of SMBreadbraw, it begins writing to the network before
+all the data has been read from disk.
+</p><p>
+This overlapping works best when the speeds of disk and network access
+are similar, having very little effect when the speed of one is much
+greater than the other.
+</p><p>
+The default value is 16384, but very little experimentation has been
+done yet to determine the optimal value, and it is likely that the best
+value will vary greatly between systems anyway. A value over 65536 is
+pointless and will cause you to allocate memory unnecessarily.
+</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2964393"></a>Max xmit</h2></div></div><div></div></div><p>
+	At startup the client and server negotiate a <i class="parameter"><tt>maximum transmit</tt></i> size,
+which limits the size of nearly all SMB commands. You can set the
+maximum size that Samba will negotiate using the <a class="indexterm" name="id2964414"></a><i class="parameter"><tt>max xmit</tt></i> option
+in <tt class="filename">smb.conf</tt>. Note that this is the maximum size of SMB requests that 
+Samba will accept, but not the maximum size that the *client* will accept.
+The client maximum receive size is sent to Samba by the client and Samba
+honours this limit.
+</p><p>
+It defaults to 65536 bytes (the maximum), but it is possible that some
+clients may perform better with a smaller transmit unit. Trying values
+of less than 2048 is likely to cause severe problems.
+</p><p>
+In most cases the default is the best option.
+</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2964453"></a>Log level</h2></div></div><div></div></div><p>
+If you set the log level (also known as <a class="indexterm" name="id2964463"></a><i class="parameter"><tt>debug level</tt></i>) higher than 2
+then you may suffer a large drop in performance. This is because the
+server flushes the log file after each operation, which can be very
+expensive. 
+</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2964483"></a>Read raw</h2></div></div><div></div></div><p>
+The <a class="indexterm" name="id2964492"></a><i class="parameter"><tt>read raw</tt></i> operation is designed to be an optimised, low-latency
+file read operation. A server may choose to not support it,
+however. and Samba makes support for <a class="indexterm" name="id2964510"></a><i class="parameter"><tt>read raw</tt></i> optional, with it
+being enabled by default.
+</p><p>
+In some cases clients don't handle <a class="indexterm" name="id2964528"></a><i class="parameter"><tt>read raw</tt></i> very well and actually
+get lower performance using it than they get using the conventional
+read operations. 
+</p><p>
+So you might like to try <a class="indexterm" name="id2964549"></a><i class="parameter"><tt>read raw</tt></i> = no and see what happens on your
+network. It might lower, raise or not affect your performance. Only
+testing can really tell.
+</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2964567"></a>Write raw</h2></div></div><div></div></div><p>
+The <a class="indexterm" name="id2964577"></a><i class="parameter"><tt>write raw</tt></i> operation is designed to be an optimised, low-latency
+file write operation. A server may choose to not support it,
+however. and Samba makes support for <a class="indexterm" name="id2964594"></a><i class="parameter"><tt>write raw</tt></i> optional, with it
+being enabled by default.
+</p><p>
+Some machines may find <a class="indexterm" name="id2964613"></a><i class="parameter"><tt>write raw</tt></i> slower than normal write, in which
+case you may wish to change this option.
+</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2964630"></a>Slow Logins</h2></div></div><div></div></div><p>
+Slow logins are almost always due to the password checking time. Using
+the lowest practical <a class="indexterm" name="id2964641"></a><i class="parameter"><tt>password level</tt></i> will improve things. 
+</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2964659"></a>Client tuning</h2></div></div><div></div></div><p>
+Often a speed problem can be traced to the client. The client (for
+example Windows for Workgroups) can often be tuned for better TCP
+performance. Check the sections on the various clients in 
+<a href="Other-Clients.html" title="Chapter 38. Samba and other CIFS clients">Samba and Other Clients</a>.
+</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2964684"></a>Samba performance problem due changing kernel</h2></div></div><div></div></div><p>
+Hi everyone. I am running Gentoo on my server and samba 2.2.8a. Recently
+I changed kernel version from linux-2.4.19-gentoo-r10 to
+linux-2.4.20-wolk4.0s. And now I have performance issue with samba. Ok
+many of you will probably say that move to vanilla sources...well I tried
+it too and it didn't work. I have 100mb LAN and two computers (linux +
+Windows2000). Linux server shares directory with DivX files, client
+(windows2000) plays them via LAN. Before when I was running 2.4.19 kernel
+everything was fine, but now movies freezes and stops...I tried moving
+files between server and Windows and it's terribly slow.
+</p><p>
+Grab mii-tool and check the duplex settings on the NIC.
+My guess is that it is a link layer issue, not an application
+layer problem.  Also run ifconfig and verify that the framing
+error, collisions, etc... look normal for ethernet.
+</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2964716"></a>Corrupt tdb Files</h2></div></div><div></div></div><p>
+Well today it happened, Our first major problem using samba.
+Our samba PDC server has been hosting 3 TB of data to our 500+ users
+[Windows NT/XP]  for the last 3 years using samba, no problem.
+But today all shares went SLOW; very slow. Also the main smbd kept
+spawning new processes so we had 1600+ running smbd's (normally we avg. 250).
+It crashed the SUN E3500 cluster twice. After a lot of searching I
+decided to <b class="command">rm /var/locks/*.tdb</b>. Happy again.
+</p><p>
+Q1) Is there any method of keeping the *.tdb files in top condition or
+how to early detect corruption?
+</p><p>
+A1) Yes, run <b class="command">tdbbackup</b> each time after stopping nmbd and before starting nmbd.
+</p><p>
+Q2) What I also would like to mention is that the service latency seems
+a lot lower then before the locks cleanup, any ideas on keeping it top notch?
+</p><p>
+A2) Yes! Same answer as for Q1!
+</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="Appendixes.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="DNSDHCP.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 38. Samba and other CIFS clients </td><td width="20%" align="center"><a accesskey="h" href="samba-doc.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 40. DNS and DHCP Configuration Guide</td></tr></table></div></body></html>