An Exchange Server 2007 server may stop processing mail and begin logging errors when the disk volume used for the Exchange Transport queue database becomes low on free disk space.
For even more detail on this topic please read A Guide to Back Pressure in Microsoft Exchange Server.
There are two key indicators of the issue:
Event ID 15002 or 15003 logged to the Application event log
Event Type: Warning
Event Source: MSExchangeTransport
Event Category: ResourceManager
Event ID: 15002
Date: 24/07/2007
Time: 1:40:03 PM
User: N/A
Computer: TESTEXC1Description:
The resource pressure is constant at MediumHigh. Statistics:
Queue database and disk space (“C:\Program Files\Microsoft\Exchange Server\TransportRoles\data\Queue\mail.que”) = 64% [MediumHigh] [Normal=61% MediumHigh=63% High=65%]
Queue database logging disk space (“C:\Program Files\Microsoft\Exchange Server\TransportRoles\data\Queue\”) = 64% [Normal] [Normal=91% MediumHigh=93% High=95%]
Version buckets = 1 [Normal] [Normal=40 MediumHigh=60 High=100]
Private bytes = 21% [Normal] [Normal=71% MediumHigh=73% High=75%]
Physical memory load = 64% [limit is 94% to start dehydrating messages.]
Inbound mail submission from the Internet, the Pickup directory, and the Replay directory has stopped. Loading of e-mail from the queuing database, if available, continues.
Inbound internet mail is not received and external messaging systems report SMTP error “4.3.1 Insufficient system resources” when connecting to your Edge Transport or Hub Transport servers
220 TESTEXC1.testing.local Microsoft ESMTP MAIL Service ready at
Tue, 24 Jul 2007 13:47:21 +1000
helo
250 TESTEXC1.testing.local Hello [10.1.1.11]
mail from: test@test.com
452 4.3.1 Insufficient system resources
The cause of this issue is free disk space falling below the normal threshold for the disk volume used by the Exchange Transport queue database. Free disk space for the Exchange Transport queue database is one of the resources monitored by the Exchange Server 2007 “Back pressure” feature. You can read a very detailed description of this feature here.
The “medium” pressure threshold is calculated by a formula as follows:
100*(hard disk drive size – 4 GB) / hard disk drive size
So for example, a 16Gb volume will have a “medium” pressure threshold of:
100*(16 – 4) / 16 = 75%
At “medium” pressure internal mail flow will still occur, however inbound internet email will not be received and any applications that use non-MAPI methods to send email (eg they use the Pickup queue) will also cease being able to send email. Anything under 4Gb of free space is automatically considered “high” pressure, which ceases all mail flow. These thresholds are configurable so that instead of relying on the formula you can hardcode the percentage values that you would like, however I don’t recommend this and I am leaving it outside the scope of this particular blog post.
However a solution I do recommend is to relocate the Exchange Transport queue database to another volume. By default the database is installed to the same location as the Exchange Server 2007 program files. For some deployments this means the C: drive, along with the operating system and other application files. With Exchange Server 2003 it was a simple enough task to relocate the MTA queue to a different volume (often a dedicated volume). The MTA would also operate quite happily as long as it had at least 10mb of free disk space. The new Exchange Transport queue database will by default require more than 4Gb of disk space, and you would size this volume according to your organisation’s requirements.
Exchange Server 2007 has a limited administrative GUI. Most simple tasks are enabled in the GUI, but more advanced tasks are only available via the Exchange Management Shell (PowerShell). Moving the Exchange Transport queue database is not even available in the shell – you need to directly edit a configuration file to make this change.
The config file is the EdgeTransport.exe.config file, located in the \bin folder of your Exchange Server 2007 program files installation (eg C:\Program Files\Microsoft\Exchange Server\bin). By default this would mean the location of the queue database is “C:\Program Files\Microsoft\Exchange Server\TransportRoles\data\Queue”.
Open up the config file and look for these entries:
<add key=”QueueDatabasePath” value = “…” />
<add key=”QueueDatabaseLoggingPath” value = “…” />
Change the path to the new location where you would like to store the database. Exchange will automatically create the new folder if it does not already exist, provided that the drive or parent folder has the correct permissions already. These are:
- Administrators – Full Control
- System – Full Control
- Network Service – Full Control
You can also manually create the new location yourself.
If you are planning to just relocate the database without copying the existing database, then simply edit and save the file, and then restart the Microsoft Exchange Transport service. If you want to retain the existing queue database, then you need to manually copy or move the files yourself, edit and save the file, and then restart the service.
If you have performed these tasks correctly and the new volume has adequate free disk space then the Exchange Transport agent will resume normal email processing.
All of these articles have saved me a lot of heheacads.
Exchange 2013 SP1 CU5
I am getting this back-pressure event (452 4.3.1 Insufficient system resources) and inbound (external) email is being delayed.
Both my system (C:) and data (D:) drive have well over 60GB free disk space – yet I keep getting this message.
Any help on where I should look to disable or correct this issue?
Thanks!
Back pressure isn’t only caused by low disk space. Event logs will record back pressure events.
Some more info:
https://www.practical365.com/exchange-transport-server-back-pressure/
Also with Exchange 2013 make sure you’re looking at the correct server role. Transport is on the Mailbox server now, so if you’ve got separate server roles installed then you’ll need to look at your Mailbox not Client Access servers.
Hi Paul,
Thank you very much for your guidance. I’m able to solve my problem yesterday.
We’re running an Exchange 2007 SP3 server with a C:-disk of only 23GB and approx. 1.5GB free storage, so we’ve run into this problem a few times, usually solved by a little cleanup and a reboot – but I really think it’s time to move the queue-database.
My question however is regarding wheter or not I should move the database-files as well? We currently have mail.que of ~340MB and 5MB log/jrs-files in the queue-folder. What services do I need to turn off before being able to move these files, and what are the results of moving/not moving these files?
Thanks in advance for your question, as well as an awesome article really comming in handy 🙂
I did a little more Googling on the subject and came across a well informed site at technet; http://technet.microsoft.com/en-us/library/bb125177(v=exchg.80).aspx
There was a Powershell-script for moving what I needed, and everything resolved in a matter of seconds 🙂
i have an issue with Exchange 2007 SP1, could you please helpme
og Name: Application
Source: MSExchangeTransport
Date: 4/16/2012 3:23:32 PM
Event ID: 15004
Task Category: ResourceManager
Level: Warning
Keywords: Classic
User: N/A
Computer: exserver.domain.local
Description:
Resource pressure increased from Medium to High.
Resource utilization of the following resources exceed the normal level:
Version buckets = 233 [High] [Normal=80 Medium=120 High=200]
Back pressure caused the following components to be disabled:
Inbound mail submission from Hub Transport servers
Inbound mail submission from the Internet
Mail submission from the Pickup directory
Mail submission from the Replay directory
Mail submission from Mailbox servers
Mail delivery to remote domains
The following resources are in the normal state:
Queue database and disk space (“H:Queuemail.que”) = 2% [Normal] [Normal=95% Medium=97% High=99%]
Queue database logging disk space (“H:Queue”) = 2% [Normal] [Normal=95% Medium=97% High=99%]
Private bytes = 3% [Normal] [Normal=71% Medium=73% High=75%]
Physical memory load = 55% [limit is 94% before message dehydration occurs.]
Event Xml:
15004
3
15
0x80000000000000
906
Application
exserver.domain.local
Medium
High
Resource utilization of the following resources exceed the normal level:
Version buckets = 233 [High] [Normal=80 Medium=120 High=200]
Back pressure caused the following components to be disabled:
Inbound mail submission from Hub Transport servers
Inbound mail submission from the Internet
Mail submission from the Pickup directory
Mail submission from the Replay directory
Mail submission from Mailbox servers
Mail delivery to remote domains
The following resources are in the normal state:
Queue database and disk space (“H:Queuemail.que”) = 2% [Normal] [Normal=95% Medium=97% High=99%]
Queue database logging disk space (“H:Queue”) = 2% [Normal] [Normal=95% Medium=97% High=99%]
Private bytes = 3% [Normal] [Normal=71% Medium=73% High=75%]
Physical memory load = 55% [limit is 94% before message dehydration occurs.]
My Hard Drive is 147 GB and I am facing Back pressure issue which states Low disk space issue, paul then how much free disk should be retained on disk to relive the issue. Secondly I have the only drive so moving queue database to other drive is not possible and also it is not recommended to disable the Back Pressure.
It is really up to you how much you want to tune the back pressure thresholds.
I’m a bit concerned that a 147Gb disk on an Exchange server is full though. What else do you have on that server taking up so much space?
Paul my disk had free space of 5 GB but still I was facing issues with inbound mails from external domains, I moved all my data to other server. Now free space was more tha 90 GB.
But how can I know, how much disk space should be retained on disk in future to keep away from problem.
Rajesh, the default threshold is 4Gb. Or at least it was when I wrote this article. I haven’t checked since then to see if a later service pack changed it at all.
Fantastic! Thanks that was the exact problem.
Shannon, the queue DB and folder can reside separately from everything else if you just want to make the changes in the post above.
Besides moving the Queue folder and files, do I need to relocate the other folders and files under the transportrole?
I really appreciate the info, I really do.
Thanks a lot
Paul, You Rock! this is just what i needed. It worked just as you said it would.. Dinner’s On me Paul, Anytime!!!
Thank you very much. This is exactly my case.