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 ><DIV
 CLASS="CHAPTER"
 ><H1
 ><A
 NAME="SPEED"
 ></A
 >Chapter 17. Samba performance issues</H1
 ><DIV
 CLASS="SECT1"
 ><H1
 CLASS="SECT1"
 ><A
 NAME="AEN2742"
 ></A
 >17.1. Comparisons</H1
 ><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"
 ><H1
 CLASS="SECT1"
 ><A
 NAME="AEN2748"
 ></A
 >17.2. Oplocks</H1
 ><DIV
 CLASS="SECT2"
 ><H2
 CLASS="SECT2"
 ><A
 NAME="AEN2750"
 ></A
 >17.2.1. Overview</H2
 ><P
 >Oplocks are the way that SMB clients get permission from a server to
 locally cache file operations. If a server grants an oplock
 (opportunistic lock) then the client is free to assume that it is the
 only one accessing the file and it will agressively cache file
 data. With some oplock types the client may even cache file open/close
 operations. This can give enormous performance benefits.</P
 ><P
 >With the release of Samba 1.9.18 we now correctly support opportunistic
 locks. This is turned on by default, and can be turned off on a share-
 by-share basis by setting the parameter :</P
 ><P
 ><B
 CLASS="COMMAND"
 >oplocks = False</B
 ></P
 ><P
 >We recommend that you leave oplocks on however, as current benchmark
 tests with NetBench seem to give approximately a 30% improvement in
 speed with them on. This is on average however, and the actual
 improvement seen can be orders of magnitude greater, depending on
 what the client redirector is doing.</P
 ><P
 >Previous to Samba 1.9.18 there was a 'fake oplocks' option. This
 option has been left in the code for backwards compatibility reasons
 but it's use is now deprecated. A short summary of what the old
 code did follows.</P
 ></DIV
 ><DIV
 CLASS="SECT2"
 ><H2
 CLASS="SECT2"
 ><A
 NAME="AEN2758"
 ></A
 >17.2.2. Level2 Oplocks</H2
 ><P
 >With Samba 2.0.5 a new capability - level2 (read only) oplocks is
 supported (although the option is off by default - see the smb.conf
 man page for details). Turning on level2 oplocks (on a share-by-share basis)
 by setting the parameter :</P
 ><P
 ><B
 CLASS="COMMAND"
 >level2 oplocks = true</B
 ></P
 ><P
 >should speed concurrent access to files that are not commonly written
 to, such as application serving shares (ie. shares that contain common
 .EXE files - such as a Microsoft Office share) as it allows clients to
 read-ahread cache copies of these files.</P
 ></DIV
 ><DIV
 CLASS="SECT2"
 ><H2
 CLASS="SECT2"
 ><A
 NAME="AEN2764"
 ></A
 >17.2.3. Old 'fake oplocks' option - deprecated</H2
 ><P
 >Samba can also fake oplocks, by granting a oplock whenever a client
 asks for one. This is controlled using the smb.conf option "fake
 oplocks". If you set "fake oplocks = yes" then you are telling the
 client that it may agressively cache the file data for all opens.</P
 ><P
 >Enabling 'fake oplocks' on all read-only shares or shares that you know
 will only be accessed from one client at a time you will see a big
 performance improvement on many operations. If you enable this option
 on shares where multiple clients may be accessing the files read-write
 at the same time you can get data corruption.</P
 ></DIV
 ></DIV
 ><DIV
 CLASS="SECT1"
 ><H1
 CLASS="SECT1"
 ><A
 NAME="AEN2768"
 ></A
 >17.3. Socket options</H1
 ><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 -O option, or in the smb.conf file.</P
 ><P
 >The "socket options" section of the smb.conf 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 "socket options = 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"
 ><H1
 CLASS="SECT1"
 ><A
 NAME="AEN2775"
 ></A
 >17.4. Read size</H1
 ><P
 >The option "read size" 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"
 ><H1
 CLASS="SECT1"
 ><A
 NAME="AEN2780"
 ></A
 >17.5. Max xmit</H1
 ><P
 >At startup the client and server negotiate a "maximum transmit" size,
 which limits the size of nearly all SMB commands. You can set the
 maximum size that Samba will negotiate using the "max xmit = " option
 in smb.conf. Note that this is the maximum size of SMB request 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"
 ><H1
 CLASS="SECT1"
 ><A
 NAME="AEN2785"
 ></A
 >17.6. Locking</H1
 ><P
 >By default Samba does not implement strict locking on each read/write
 call (although it did in previous versions). If you enable strict
 locking (using "strict locking = yes") then you may find that you
 suffer a severe performance hit on some systems.</P
 ><P
 >The performance hit will probably be greater on NFS mounted
 filesystems, but could be quite high even on local disks.</P
 ></DIV
 ><DIV
 CLASS="SECT1"
 ><H1
 CLASS="SECT1"
 ><A
 NAME="AEN2789"
 ></A
 >17.7. Share modes</H1
 ><P
 >Some people find that opening files is very slow. This is often
 because of the "share modes" code needed to fully implement the dos
 share modes stuff. You can disable this code using "share modes =
 no". This will gain you a lot in opening and closing files but will
 mean that (in some cases) the system won't force a second user of a
 file to open the file read-only if the first has it open
 read-write. For many applications that do their own locking this
 doesn't matter, but for some it may. Most Windows applications
 depend heavily on "share modes" working correctly and it is
 recommended that the Samba share mode support be left at the
 default of "on".</P
 ><P
 >The share mode code in Samba has been re-written in the 1.9.17
 release following tests with the Ziff-Davis NetBench PC Benchmarking
 tool. It is now believed that Samba 1.9.17 implements share modes
 similarly to Windows NT.</P
 ><P
 >NOTE: In the most recent versions of Samba there is an option to use
 shared memory via mmap() to implement the share modes. This makes
 things much faster. See the Makefile for how to enable this.</P
 ></DIV
 ><DIV
 CLASS="SECT1"
 ><H1
 CLASS="SECT1"
 ><A
 NAME="AEN2794"
 ></A
 >17.8. Log level</H1
 ><P
 >If you set the log level (also known as "debug level") 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"
 ><H1
 CLASS="SECT1"
 ><A
 NAME="AEN2797"
 ></A
 >17.9. Wide lines</H1
 ><P
 >The "wide links" option is now enabled by default, but if you disable
 it (for better security) then you may suffer a performance hit in
 resolving filenames. The performance loss is lessened if you have
 "getwd cache = yes", which is now the default.</P
 ></DIV
 ><DIV
 CLASS="SECT1"
 ><H1
 CLASS="SECT1"
 ><A
 NAME="AEN2800"
 ></A
 >17.10. Read raw</H1
 ><P
 >The "read raw" 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 "read raw" optional, with it
 being enabled by default.</P
 ><P
 >In some cases clients don't handle "read raw" 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 "read raw = 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"
 ><H1
 CLASS="SECT1"
 ><A
 NAME="AEN2805"
 ></A
 >17.11. Write raw</H1
 ><P
 >The "write raw" 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 "write raw" optional, with it
 being enabled by default.</P
 ><P
 >Some machines may find "write raw" slower than normal write, in which
 case you may wish to change this option.</P
 ></DIV
 ><DIV
 CLASS="SECT1"
 ><H1
 CLASS="SECT1"
 ><A
 NAME="AEN2809"
 ></A
 >17.12. Read prediction</H1
 ><P
 >Samba can do read prediction on some of the SMB commands. Read
 prediction means that Samba reads some extra data on the last file it
 read while waiting for the next SMB command to arrive. It can then
 respond more quickly when the next read request arrives.</P
 ><P
 >This is disabled by default. You can enable it by using "read
 prediction = yes".</P
 ><P
 >Note that read prediction is only used on files that were opened read
 only.</P
 ><P
 >Read prediction should particularly help for those silly clients (such
 as "Write" under NT) which do lots of very small reads on a file.</P
 ><P
 >Samba will not read ahead more data than the amount specified in the
 "read size" option. It always reads ahead on 1k block boundaries.</P
 ></DIV
 ><DIV
 CLASS="SECT1"
 ><H1
 CLASS="SECT1"
 ><A
 NAME="AEN2816"
 ></A
 >17.13. Memory mapping</H1
 ><P
 >Samba supports reading files via memory mapping them. One some
 machines this can give a large boost to performance, on others it
 makes not difference at all, and on some it may reduce performance.</P
 ><P
 >To enable you you have to recompile Samba with the -DUSE_MMAP option
 on the FLAGS line of the Makefile.</P
 ><P
 >Note that memory mapping is only used on files opened read only, and
 is not used by the "read raw" operation. Thus you may find memory
 mapping is more effective if you disable "read raw" using "read raw =
 no".</P
 ></DIV
 ><DIV
 CLASS="SECT1"
 ><H1
 CLASS="SECT1"
 ><A
 NAME="AEN2821"
 ></A
 >17.14. Slow Clients</H1
 ><P
 >One person has reported that setting the protocol to COREPLUS rather
 than LANMAN2 gave a dramatic speed improvement (from 10k/s to 150k/s).</P
 ><P
 >I suspect that his PC's (386sx16 based) were asking for more data than
 they could chew. I suspect a similar speed could be had by setting
 "read raw = no" and "max xmit = 2048", instead of changing the
 protocol. Lowering the "read size" might also help.</P
 ></DIV
 ><DIV
 CLASS="SECT1"
 ><H1
 CLASS="SECT1"
 ><A
 NAME="AEN2825"
 ></A
 >17.15. Slow Logins</H1
 ><P
 >Slow logins are almost always due to the password checking time. Using
 the lowest practical "password level" will improve things a lot. You
 could also enable the "UFC crypt" option in the Makefile.</P
 ></DIV
 ><DIV
 CLASS="SECT1"
 ><H1
 CLASS="SECT1"
 ><A
 NAME="AEN2828"
 ></A
 >17.16. Client tuning</H1
 ><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.</P
 ><P
 >See your client docs for details. In particular, I have heard rumours
 that the WfWg options TCPWINDOWSIZE and TCPSEGMENTSIZE can have a
 large impact on performance.</P
 ><P
 >Also note that some people have found that setting DefaultRcvWindow in
 the [MSTCP] section of the SYSTEM.INI file under WfWg to 3072 gives a
 big improvement. I don't know why.</P
 ><P
 >My own experience wth DefaultRcvWindow is that I get much better
 performance with a large value (16384 or larger). Other people have
 reported that anything over 3072 slows things down enourmously. One
 person even reported a speed drop of a factor of 30 when he went from
 to 8192. I don't know why.</P
 ><P
 >It probably depends a lot on your hardware, and the type of unix box
 you have at the other end of the link.</P
 ><P
 >Paul Cochrane has done some testing on client side tuning and come
 to the following conclusions:</P
 ><P
 >Install the W2setup.exe file from www.microsoft.com. This is an
 update for the winsock stack and utilities which improve performance.</P
 ><P
 >Configure the win95 TCPIP registry settings to give better
 perfomance. I use a program called MTUSPEED.exe which I got off the
 net. There are various other utilities of this type freely available.
 The setting which give the best performance for me are:</P
 ><P
 ></P
 ><OL
 TYPE="1"
 ><LI
 ><P
 >MaxMTU                  Remove</P
 ></LI
 ><LI
 ><P
 >RWIN                    Remove</P
 ></LI
 ><LI
 ><P
 >MTUAutoDiscover         Disable</P
 ></LI
 ><LI
 ><P
 >MTUBlackHoleDetect      Disable</P
 ></LI
 ><LI
 ><P
 >Time To Live            Enabled</P
 ></LI
 ><LI
 ><P
 >Time To Live - HOPS     32</P
 ></LI
 ><LI
 ><P
 >NDI Cache Size          0</P
 ></LI
 ></OL
 ><P
 >I tried virtually all of the items mentioned in the document and
 the only one which made a difference to me was the socket options. It
 turned out I was better off without any!!!!!</P
 ><P
 >In terms of overall speed of transfer, between various win95 clients
 and a DX2-66 20MB server with a crappy NE2000 compatible and old IDE
 drive (Kernel 2.0.30). The transfer rate was reasonable for 10 baseT.</P
 ><P
 >FIXME
 The figures are:          Put              Get
 P166 client 3Com card:    420-440kB/s      500-520kB/s
 P100 client 3Com card:    390-410kB/s      490-510kB/s
 DX4-75 client NE2000:     370-380kB/s      330-350kB/s</P
 ><P
 >I based these test on transfer two files a 4.5MB text file and a 15MB
 textfile. The results arn't bad considering the hardware Samba is
 running on. It's a crap machine!!!!</P
 ><P
 >The updates mentioned in 1 and 2 brought up the transfer rates from
 just over 100kB/s in some clients.</P
 ><P
 >A new client is a P333 connected via a 100MB/s card and hub. The
 transfer rates from this were good: 450-500kB/s on put and 600+kB/s
 on get.</P
 ><P
 >Looking at standard FTP throughput, Samba is a bit slower (100kB/s
 upwards). I suppose there is more going on in the samba protocol, but
 if it could get up to the rate of FTP the perfomance would be quite
 staggering.</P
 ></DIV
 ><DIV
 CLASS="SECT1"
 ><H1
 CLASS="SECT1"
 ><A
 NAME="AEN2860"
 ></A
 >17.17. My Results</H1
 ><P
 >Some people want to see real numbers in a document like this, so here
 they are. I have a 486sx33 client running WfWg 3.11 with the 3.11b
 tcp/ip stack. It has a slow IDE drive and 20Mb of ram. It has a SMC
 Elite-16 ISA bus ethernet card. The only WfWg tuning I've done is to
 set DefaultRcvWindow in the [MSTCP] section of system.ini to 16384. My
 server is a 486dx3-66 running Linux. It also has 20Mb of ram and a SMC
 Elite-16 card. You can see my server config in the examples/tridge/
 subdirectory of the distribution.</P
 ><P
 >I get 490k/s on reading a 8Mb file with copy.
 I get 441k/s writing the same file to the samba server.</P
 ><P
 >Of course, there's a lot more to benchmarks than 2 raw throughput
 figures, but it gives you a ballpark figure.</P
 ><P
 >I've also tested Win95 and WinNT, and found WinNT gave me the best
 speed as a samba client. The fastest client of all (for me) is
 smbclient running on another linux box. Maybe I'll add those results
 here someday ...</P
 ></DIV
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657 lines

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