Speaking to BES support, I am without a difinative answer.
The question is: At what point should I consider moving from MSDE to SQL?

Is the answer: The amount of handhelds on the BES (ie. >300?)
Is the answer: The performance issues

I have been told some companies have to move to SQL due to performance hit... because of the manner in which the users operate..with only 100 users.
And, some companies are still running fine on MSDE with over 400 users.

Thoughts? Comments? Limericks?

bump

There is a limit of two mail agents on the BlackBerry Enterprise Server when using the Microsoft Data Engine (MSDE) for the BlackBerry® Configuration Database. As a result, the stability of the BlackBerry Enterprise Server may be compromised when running more than two Exchange Servers.

To improve stability, the BlackBerry Enterprise Server attempts to divide the mail agents among the mail servers. With an increased number of mail servers, communication with one mail server may affect communication for BlackBerry device users on another mail server. In these situations, consideration should be given to utilizing the SQL Server to take advantage of an increased number of mail agents.

Each agent can handle 500 users max.

So you can run up to 1000 users with MSDE (2 agents max) if your hardware can handle it. You should monitor MSDE performance after a few hundred users. Most people notice after 500 users performance goes down and switch to SQL to lessen the load on the busy BES server. And if you have 500 users you can probably afford SQL. When I switched to SQL I noticed a decent drop in used resources on the BES.

IIRC it is a good idea to keep no more than 500 BES users per mail server due to the overhead that BES creates. each BES users is about 3.76 mail box users addittional load.

SQL can handle 5 mail agents and BES 4.1 can handle up to 2000 users supporting 5 mail servers (more than that requires RIM's help)

The "stability" issue comes into effect when you've got highly utilized agents with several mail servers ... this is due to a governor put in place with MSDE 2000. There is a limit to 8 concurrent connections. You can use more than 2 mail servers; you can actually add more than the 2 mailbox agents ... but doing so puts each agent into more contention with the other.

Note: If you move from MSDE to SQL, check out KB12247; specifically Procedure 2 Task 4.

By default. You can increase the number of users an agent can handle ... you can also decrease the number of users an agent can handle ... NumAgents registry key.

I would still never recommend more than a few hundred on MSDE ... and even at that, depending on how important recovery from failure is for you, you might look to go to a separate sql server sooner ... or at least implement a simple yet effective backup procedure for your MSDE database.

This depends on the environment. I had an environment with 4000 users on a single 4.1 SP2 BES and it performed fine with the 5 default agents... granted the user load was minimal and all they used was email; no PIM data. If you've got a few heavy mailbox users you might see issues at 50 users with a single mailbox agent. They key is to monitor your performance of your mail servers. With Exchange 2003 each BES user is anywhere from 1-16x the load of a non-BES user ... with Exchange 2007 and 2010 those numbers are potentially 2x or more.

SQL can handle many more than 5 agents per given BES. Yes a standard Exchange BES according to RIM indicates that it supportes up to 2000 users ... but I don't know many people that put 2000 users on a single BES; usually more like 1200 max. That said, you can also have more than 5 mailbox servers communicating with a single BES ... especially if you increase the NumAgents registry key previously mentioned.

Then ... you could always also go to SQL Express 2005 which doesn't have a workload governor like MSDE 2000. It does have a limit of 1GB memory utilization and 4GB database size (MSDE is 2GB database size limit)

SQL2008 Express FTW.

If I ever reinstall I'll be using it instead of SQL2005 Express which is what I'm using now.

... as long as you don't mind not being supported.

Meh, I'm not being supported now!

Same here, you folks are my support!