Exchange Server 2007 Down due to Insufficient System Resource

Environment: Exchange Server 2007 SP1 with BES (BlackBerry Enterprise Server)
VMWare ESX Server 3.5.0

BES User was unable to send/receive mail from their BB.

Investigation:

- check BES server = OK
- check OWA/WebMail = inaccessible
- check Exchange Management = OK (services UP)
- telnet to exchange server port 25 = NOK --> Insufficient Resource
- check Exchange Server resource = Memory OK, but DISK FREE SPACE 'only' 140MB

discovered that Exchange Server 2007 has a 'Back Pressure'

In Exchange Server 2007, the Transport service monitors system resources such as disk space and memory on Transport servers (the Hub Transport and the Edge Transport servers), and stops message submission if it is running low on these resources. It continues to deliver existing messages in the queue. When resource utilization returns to normal, it resumes message submission. The feature is called Back Pressure.

The Back Pressure settings in Exchange Server 2007 RTM stop inbound mailflow if free disk space is below 4 Gigs. This static threshold has been lowered in SP1 to a more realistic 500 Mb.

Resolution:

- purge/delete some unused files, but free space still < 500Mb.
- Create new disk partition (idea to change mail.queue & logs to new path):
1. Stop BES
2. Shutdown Exchange Server
3. Add New Disk (10GB) from VMWare Infrastructure Client
4. Startup Exchange Server, format new disk from DiskManagement (control panel)
4. Re-configure Queue & Log path location, do backup original config (safety first!)
C:\Program Files\Microsoft\Exchange Server\Bin\EdgeTransport.exe.config

use notepad, change LocalPath value:

add key="QueueDatabasePath" value="LocalPath"
add key="QueueDatabaseLoggingPath" value="LocalPath"

i.e:
from add key="QueueDatabasePath" value="C:\original_path"
add key="QueueDatabaseLoggingPath" value="C:\original_path"
to add key="QueueDatabasePath" value="E:\Queue\QueueDB"
add key="QueueDatabaseLoggingPath" value="E:\Queue\QueueLogs"



5. Restart Exchange Transport Services (new mail.queue, log, chk, jrs created on new location)
6. Verify that the new Mail.que and Trn.chk files are created at the new location.
7. Verify that the new Trn.log, Trntmp.log, Trnres00001.jrs, Trnres00002.jrs, and Temp.edb files are created at the new location.
6. Move old/unused Mail.queue, Log, jrs, chk from original location to new disk (for backup only, in any case you will need it, actually you can delete it permanently)
7. Start BES service
8. Check that Exchange OWA/POP/SMTP & BES back to normal