[Samba] Samba PDC + OpenLDAP + Samba BDC

John H Terpstra jht at samba.org
Fri Feb 18 14:58:09 GMT 2005

On Friday 18 February 2005 06:05, Robert Becskei wrote:
> Hello everyone,
>  the time for me to use a OpenLDAP server is getting closer ( :( yikes..I'm
> still scared sorta) ,
>  I currently have a Samba PDC with tdbsam with 50 users goes fine, our
> company will grow (doing our best)
> in this year by a minimum of 25-30 computers, and I've stuided the TOSHARG
> , and it says that for every
> 50 computer a bdc is suggested.

I wrote that advice and it believe it has been updated in the on-line version 
available from:

Do not take that guideline as cast in stone. Most sites can get away with much 
more than that. I know of sites with around 500 windows clients and just a 

The key determinants of how many xDCs are needed are:
	a. Network band-width
	b. Load level on the DCs

If the network bandwidth usage is low and the load on the PDC is relatively 
low you may get away with 500 or more windows clients without any BDCs.

> The questions :
>  1.how does the client who is logging in to the domain know which server to
> use pdc bdc1 bdc2 ? , how is this decided.

Usually from WINS.

>  2.is it a good idea to place the pdc and bdc close to each other , on the
> same switch ? , or should they be far from each other
> (closer to the clients they are supposed to validate in the domain).

The old advice with NT4 was to have a PDC and a BDC on the one subnet and then 
at least one BDC per subnet. But you shoud first check to see if you really 
need to indulge in the complexity of adding a BDC. The sure sign is when you 
start to get sporadic network logon failures that succeed on the second oor 
third retry.

The failure message on the client that gives the tell-tale is a message that a 
domain controller could not be found.

>  Thank you foreward for your time.
>  Sincerely
>  Robert Becskei

I hope this helps.

- John T.
John H Terpstra
Samba-Team Member
Phone: +1 (650) 580-8668

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