7. Optimization of Samba services.

Contents of this section

Samba has a number of parameters which allow for tuning your SMB network.
They may work to cross-purposes and local requirements may differ so you
will have to experiment.

7.1 Memory usage

Keep also in mind that Samba spawns a new smbd process for every client
connection, which does take some memory (you may count usually about 800K
for the first client plus some memory used for caching). How big the
increments are may depend on how shared libraries are used, if at all. Also
important is how good your OS is at overlapping the text part of different
processes, etc. One of the possible optimizations may consist of adding
more memory to a server or splitting the server's job between more
machines. Normally, after about 25 active clients, this is advisable,
unless your server has a lot of CPU and memory horsepower. Bear in mind,
however, that if you have 50 possible clients, probably only a few of them
may be logged into the server at any given time.

The rate with which clients gobble server memory, and the level where it is
going to stop, depends to a great degree on how many open, and how big,
directories are cached in memory. Some clients do not close directories
when they are done and memory usage grows and grows. You may change the
MAXDIR constant in local.h to keep Samba from caching too much. An absolute
minimum for a correct operation is 2 but with low values complex operations
on deep directory trees may fail. 64 is the default as of the 1.9.15p5
patchlevel of Samba. Andrew Tridgell wrote: "Note that samba does try to
allow up to 256 open directories even if MAXDIR is much smaller. It does
this by assuming the directory doesn't change on disk and 'idling' then by
noting only the path name in memory and reopening it when needed. This will
fail if the client is deleting files in a directory that it has open from a
previous search, then continuing the search in that directory. In this case
the client can get confused. To combat this samba always idles the
directory that is least recently used." Also MAX_CONNECTIONS and
MAX_OPEN_FILES have some memory impact, even when entries are not in use.
These limits are per client and not server wide.

7.2 Tuning

Check the smb.conf manual page for details, but here are some parameters
(some of them are tune-up parameters in a rather broad sense) that you may
want to read about:

   * dead time
   * keep alive
   * max disk size
   * max connections
   * min print space
   * wide links
   * read raw
   * write raw
   * getwd cache
   * lpq cache time
   * read prediction
   * read size
   * socket options

Available socket options, their behaviour and interpretations may depend on
the underlying sockets implementation. Consult your library documentation
for details.

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