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| author | Jelmer Vernooij <jelmer@samba.org> | 2003-09-23 21:24:11 +0000 |
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| committer | Jelmer Vernooij <jelmer@samba.org> | 2003-09-23 21:24:11 +0000 |
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diff --git a/docs/htmldocs/speed.html b/docs/htmldocs/speed.html new file mode 100644 index 0000000000..b55989d053 --- /dev/null +++ b/docs/htmldocs/speed.html @@ -0,0 +1,141 @@ +<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="index.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"><<a href="mailto:paulc@dth.scot.nhs.uk">paulc@dth.scot.nhs.uk</a>></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"><<a href="mailto:jelmer@samba.org">jelmer@samba.org</a>></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"><<a href="mailto:jht@samba.org">jht@samba.org</a>></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#id2976235">Comparisons</a></dt><dt><a href="speed.html#id2976281">Socket Options</a></dt><dt><a href="speed.html#id2976372">Read Size</a></dt><dt><a href="speed.html#id2976422">Max Xmit</a></dt><dt><a href="speed.html#id2976477">Log Level</a></dt><dt><a href="speed.html#id2976507">Read Raw</a></dt><dt><a href="speed.html#id2976592">Write Raw</a></dt><dt><a href="speed.html#id2976655">Slow Logins</a></dt><dt><a href="speed.html#id2976683">Client Tuning</a></dt><dt><a href="speed.html#id2976707">Samba Performance Problem Due to Changing Linux Kernel</a></dt><dt><a href="speed.html#id2976766">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="id2976235"></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 an NT or Windows for Workgroups 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 depends on your system. +</p><p> +Several people have done comparisons between Samba and Novell, NFS or +Windows NT. In some cases Samba performed the best, in others the worst. I +suspect the biggest factor is not Samba versus 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="id2976281"></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="id2976313"></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 correct 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="id2976350"></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="id2976372"></a>Read Size</h2></div></div><div></div></div><p> +The option <a class="indexterm" name="id2976382"></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 little effect when the speed of one is much +greater than the other. +</p><p> +The default value is 16384, but little experimentation has been +done as 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="id2976422"></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="id2976442"></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 +honors 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. +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="id2976477"></a>Log Level</h2></div></div><div></div></div><p> +If you set the log level (also known as <a class="indexterm" name="id2976487"></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 quite +expensive. +</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2976507"></a>Read Raw</h2></div></div><div></div></div><p> +The <a class="indexterm" name="id2976517"></a><i class="parameter"><tt>read raw</tt></i> operation is designed to be an optimized, low-latency +file read operation. A server may choose to not support it, +however, and Samba makes support for <a class="indexterm" name="id2976534"></a><i class="parameter"><tt>read raw</tt></i> optional, with it +being enabled by default. +</p><p> +In some cases clients do not handle <a class="indexterm" name="id2976552"></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="id2976573"></a><i class="parameter"><tt>read raw</tt></i> = no and see what happens on your +network. It might lower, raise or not effect 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="id2976592"></a>Write Raw</h2></div></div><div></div></div><p> +The <a class="indexterm" name="id2976602"></a><i class="parameter"><tt>write raw</tt></i> operation is designed to be an optimized, low-latency +file write operation. A server may choose to not support it, however, and Samba makes support for +<a class="indexterm" name="id2976618"></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="id2976637"></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="id2976655"></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="id2976666"></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="id2976683"></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 +<link linkend="Other-Clients">. +</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2976707"></a>Samba Performance Problem Due to Changing Linux Kernel</h2></div></div><div></div></div><p> +A user wrote the following to the mailing list: +</p><p> +I am running Gentoo on my server and Samba 2.2.8a. Recently +I changed kernel version from <tt class="filename">linux-2.4.19-gentoo-r10</tt> to +<tt class="filename">linux-2.4.20-wolk4.0s</tt>. And now I have a performance issue with Samba. +Many of you will probably say, “<span class="quote">Move to vanilla sources!</span>” +Well, I tried that and it didn't work. I have a 100mb LAN and two computers (Linux and +Windows 2000). The Linux server shares directories with DivX files, the client +(Windows 2000) plays them via LAN. Before when I was running the 2.4.19 kernel +everything was fine, but now movies freeze and stop. I tried moving +files between the server and Windows and it is terribly slow. +</p><p> +The answer he was given is: +</p><p> +Grab the 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, and so on, look normal for ethernet. +</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2976766"></a>Corrupt tdb Files</h2></div></div><div></div></div><p> +Our Samba PDC server has been hosting three TB of data to our 500+ users +[Windows NT/XP] for the last three years using Samba without a problem. +Today all shares went 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> +<span class="emphasis"><em>Question:</em></span> Is there any method of keeping the *.tdb files in top condition or +how can I detect early corruption? +</p><p> +<span class="emphasis"><em>Answer:</em></span> Yes, run <b class="command">tdbbackup</b> each time after stopping nmbd and before starting nmbd. +</p><p> +<span class="emphasis"><em>Question:</em></span> What I also would like to mention is that the service latency seems +a lot lower than before the locks cleanup. Any ideas on keeping it top notch? +</p><p> +<span class="emphasis"><em>Answer:</em></span> Yes. Same answer as for previous question! +</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="index.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 40. DNS and DHCP Configuration Guide</td></tr></table></div></body></html> |