[Samba] Samba 2.2.8a and 3.0.0

John H Terpstra jht at samba.org
Sat Oct 18 16:59:48 GMT 2003

On Sat, 18 Oct 2003, William Jojo wrote:

> Samba Team,
> How do I create simulated load on a samba server? I wish to use
> feedback-directed program restructuring on AIX 5.2 to determine if
> performance can be improved by rearranging the executable generated by the
> IBM 6.0 compiler.

I am forwarding this reply to someone who may be prompted to follow up
with you regarding performance metrics.

> Mostly I'm determining what the upper bound on smbd's is in a
> multiprogramming environment. I'm currently running about between 800 and
> 1000 smbd's a day on a 6-way 6H1 (RS64-III) with 24GB memory and 800 GB of
> attached SSA disk for roaming profiles. All of this is being done with
> 2.2.8a.

I'd love to see what your resource consumption levels are.

> I'm setting up my 3.0.0 test area on similar hardware, but wanted insight
> from the experts on what you've done already to improve internal
> performance as my approach is to improve cache hit ratio and translation
> look-aside.
> I've already tuned every piece of hardware to my abilities and even
> implemented write-behind algorithms. I'm basically wringing out the towel
> to see if there are any drops of peformance left to be found.
> Are there any internal limitations with the TDB's, et al, where there may
> be an upper bound on concurrent smbd's?

I have done some limited qualitative work only with tdbsam compared with
smbpasswd. The performance improvement with about 1100 entries was
significant. Parsing of the smbpasswd file causes quite a hit when there
are gazillions of entries. Use of tdbsam or ldapsam becomes quite
attractive as the number of account entries increases.

> Also are there any internal performance enhancements for smbpasswd files
> of >15000 entries?
> We are looking at LDAP for storing passwords. What kind of improvement can
> I expect when moving passwords from a flat file to a dynamic container?

You might also check the performance of the 'tdbsam' facility that is
available with samba-3.0.x. You can use the 'pdbedit' tool to migrate your
existing smbpasswd file to the tdbsam passdb.tdb file.

In the Samba-HOWTO-Collection.pdf you will see a recommendation to use
LDAP if there are more than 250 users. This recommendation has nothing to
do with the efficiency of tdbsam, but was made considering the likelihood
that with 250 or more users you may need to use PDC/BDC configuration.
When you need a Samba-BDC it becomes essential that you have the ability
to synchronize the password database - something that becomes very
difficult with tdbsam, but is easily accomplished with an LDAP backend.

> On a related note, you guys rock! You are the reason we can do the above
> with one server! You have saved us hundreds of thousands of US $'s on
> licensing and servers alone! Your technical prowess is appreciated far
> more than you know!


- John T.
John H Terpstra
Email: jht at samba.org

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