SMB2 questions

Christopher R. Hertel crh at
Wed Aug 10 12:51:33 MDT 2011

Volker Lendecke wrote:
> On Tue, Aug 09, 2011 at 12:32:36PM -0600, Jeff Sadowski wrote:
>> Reading through the release notes today I saw the section about SMB2
>> being supported but needs to be activated and tested.
>> Forgive my ignorance but what sort of things would I be looking for
>> that SMB2 does that it wouldn't do without it?
>> What sort of things would I be looking at that might break?
>> I'm guessing just anything and if something breaks ask here right?
>> Is there a good place to turn that says specifically what has changed?
>> I'm guessing that it should talk more grammatically correct to windows
>> machines and be more transparent (as another windows machine) to the
>> windows machines than before?
>> Would file sharing work any faster? I'm guessing no because that
>> should be handled by cifs right?
>> On the other hand would SMB2 be responsible for authenticating for the file?
>> Should I look for more features from a windows machine that would not
>> exist without smb2?
> The main new feature very likely will be better performance.
> The Windows SMB1 stack has not seen any performance
> improvements for quite a long time. The SMB2 client was the
> focus of development in the past years, including a lot of
> performance improvements.

The SMB1 protocol includes support for DOS and OS/2 semantics, including
OS/2 system calls.  There are also fields in many of the commands that are
there to support features and behaviors that are no longer in mainstream usage.

SMB2 removes all of that.  It was created by Microsoft for use with modern
(Vista and above) Windows systems and focuses on the abilities and features
of those systems, leaving out support for older platforms (including older
Windows platorms).

The older systems still work, they just negotiate SMB1 protocol instead of SMB2.

The command set reduction is most notable.  SMB1 has upward of 70 different
commands, while SMB2 uses about 20 (check me on the numbers).  In addition,
SMB2 implementations from Microsoft have much better support for command
chaining, which can improve response time over Wide Area connections.

I will mention that Volker did a lot of very impressive work in Samba, and
demonstrated that proper use of command chaining in SMB1 can produce very
good results.  The limitation is that both client and server need to support
long SMB1 chains.  With SMB2, the expectation that long chains are supported
is there so we are less likely to see incompatibilities.

...assuming people test the work that's been done.

Chris -)-----

"Implementing CIFS - the Common Internet FileSystem" ISBN: 013047116X
Samba Team --     -)-----   Christopher R. Hertel
jCIFS Team --   -)-----   ubiqx development, uninq.
ubiqx Team --     -)-----   crh at
OnLineBook --    -)-----   crh at

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