Friday, December 21, 2007

BES and Worker-Treats

The way Blackberry server discovers the mailboxes for the BES users by using MAPI and rapping worker treats into the MAPI session. Worker treats are processes build into the BES server, to discover and establish state full connection to the hidden BES mailbox on the each user mailbox. Each BES server is capable of handling 100 worker treads and up to 2000 users.

Mailbox moved within the same server, from one mail store to another one, will break the BB connection for the user got moved, due to limitation build into the BES user mailbox discovery process. Because BES scans users mailboxes for changes in the Server DN (distinguish name).

Blackberry Server normally generates 3 to 4 times more MAPI traffic then a regular MAPI user. The BES is being used in conjunction with latency caused severe problems. Not also BES experience but also other aspect of the network will suffer as consequence of this problem.

The size of the mailbox is not what causes the latency but specifically the number of items in your Outlook folders. The number of open items results the same behavior in poor outlook experience the famous Christmas balloon "exchange is retrieving data from such exchange server" everyone's favorite message will appears from the outlook.

Happy Holidays


Oz ozugurlu


Howie said...

One key thing to note here is that the 3-4 times more traffic than a regular MAPI user isn't an "apples to apples" comparison, but rather comparing an Outlook Cached-Mode client to a BES user (which is a non-cached MAPI connection).

To go into a bit more depth ...

Each BES will start up by default 5 dynamic mailbox agents ... each mailbox agent has a maximum of 100 MAPI threads and a maximum of 5 threads per pool. As the number of handhelds on a BES increase ... the ratio of users per thread increase, which generates a higher load on Exchange. The key is to minimize the number of Exchange servers interacting with BlackBerry servers ... and if you have multiple of each doing load balancing you're better off keeping a 50/50 load of bes / exchange users across each server than an 80/20 distribution.

As a general rule we try to allocate no more than 5 exchange servers to a single BES ... giving each mailbox agent only one mail server to deal with. obviously this'll change with quantities of users, but in general you're better off with 2 servers interacting with 5 Exchange servers each than BES interacting with 9 Exchange servers and the other interacting with just 1.

Happy BES'ing!

Oz Ozugurlu said...

Thanks Howie, nice to get detailed information as always. Marry Xmas and happy holidays