Roughly how many users should Samba 4.0 be able to handle?

[Michael Wood]

Hi

Thanks for the reply.

On 17 January 2013 22:03, Matthieu Patou <mat at samba.org> wrote:
> On 01/17/2013 06:47 AM, Michael Wood wrote:
>> I'm trying to get an idea of how many users a Samba 4.0 server should be
>> able to handle.
>>
>> In the past (one of the alphas) I tried adding about 40000 users and Samba
>> slowed to a crawl.  I can't remember the details.  Just that I had to roll
>> back to by last backup to fix the performance again.
>
> So due to indexing 40 000 users will result into 200 000 ldb entries at
> least and I suspect 400 000 worst case.

Ouch!  That sounds like a lot.

> I think it highly depend on the workload that you have.
> If you have more than 1 DC it will be slow quite quickly because DCs keeps
> on asking each other for changes (I think it's every 15s but it's tuneable)
> and this kind of search is not indexed yet (we are doing something like
> '(usnchanged>=max_usn_from_last_replication)').

OK, I currently have only one DC.  This is only for authentication.
There are no workstations joined to the domain or anything like that.
Authentication is done from a few services using LDAP.

There are very few groups with just about all users in one of the
groups and a few of the users in some other groups in addition.

So the authentication process generally just does a bind as the user
(all users are in the same OU) and then checks that they are in the
group needed for accessing the service.

> The good news is that I have a clear idea on how to implement indexing for
> this and this should start right after the first set of optimization are
> pushed.
>
> If you have 1 DC and very selective query (ideal is just basedn query) then
> I don't think that doing tdb search in a 400 000 will be that bad but I will
> let tdb expert(s) give their pov but you are rarely in this case, and
> queries that looked selective (ie. base=MYOUWITH2USERS,DC=domain,DC=tld) are
> currently not so selective (but my patches are changing this).

OK, thanks.  I think a simple bind of a DN should be quite selective :)

> I would love to do some tunning on big databases if someone can provide us a
> script to create a realistic big database (ie. not all users are called
> fooxxxx and not just 2 attributes are set) it will for sure help the
> process.

Well, I'm not sure how "realistic" mine would be, despite being quite real :)

>> I've compiled 4.0.1 and am busy adding 5000 users to my 1200 existing
>> users
>> (but on a test machine) to see what happens, but if anyone is running
>> Samba
>> 4.0 with large numbers of users I'd like to hear about it.
>>
>> Also, I know Matthieu's been working on optimising the ldb indexing code.
>> Has that made it to master yet?
>
> No but it's in process, feel free to try my ldb_perfs branch in my git repo
> to see.

I tested adding 5000 users to the existing 1200 and it did not seem to
have an impact on the speed.  I am not planning to try 40000 again
soon, though.

-- 
Michael Wood <esiotrot at gmail.com>