Several readers responded to Wednesday's article about large numbers of Entourage users degrading Exchange Server performance. After some testing, the author concluded that there is a problem with the way Microsoft implemented WevDAV. Several readers agreed, pointing to Microsoft knowledgebase articles and their own experience. Several readers also provide some techniques that help. One reader, however is not seeing the problem with 120 Entourage clients.
Ben Lachoff agrees, and said that Microsoft has verified this and has called it a "design flaw" in Exchange:
We have recently grappled with this issue at several clients, and the issue does not happen just by having Entourage clients; we have had servers with 200 Entourage users without any problems. The server slowdown ONLY happens when you move mailboxes or defrag the Exchange database on an exchange box with lots of Entourage users. These actions will cause the exchange database .stm file to be converted back into an .edb file. When the Entourage users access their exchange data after either a mailbox move or information store defrag the Entourage client software will start slowly converting all emails out of the edb file back into the stm file. This causes the server to CRAWL. You can confirm this is happening in a variety of ways, including the performance tests that Robert Liebsch mentions in his write up. You can also test with no Entourage clients open on the network and the server magically returns to normal speeds. Finally, you can check on the relative sizes of the edb/stm files and see the stm file is growing slowly over time while the edb file size gets smaller.
We called Microsoft to discuss the issue and they are aware of it. They are calling it a DESIGN FLAW in Exchange, and they currently have no time frame on a fix. The issue affects Exchange 2000, Exchange 2003, and Exchange 2007. There are similar implications for servers that are heavily used by OWA, POP3, and IMAP users, not just Entourage users.
For more info on this issue, please refer to the following articles from Microsoft: KB329067 and KB317722
There are a few ways to work around the performance issues, but they do not entirely solve the issue. One way to partially resolve the issue is to move Entourage users mailboxes to an information store on a different server or a different drive on the same server. This will help to isolate the heavy disk I/O away from the rest of the system. Another workaround is to add the DAV key suggested in KB329067 and set the value to 1GB (the maximum) This will stop WebDAV clients like Entourage from converting every email in their mailbox to the .stm file, but it will not totally resolve the issues.
Another possible solution would be to implement something like Kerio Mail Server for the Entourage users and try to integrate that into your existing Exchange environment.
Arne has some suggestions:
Just saw your article and I'd like to commiserate with Robert Liebsch.
The issue that we have found at the bottom of it is the conversion from MIME (Entourage, stm) to MAPI (Outlook, edb) and vice-versa. For us the issue is amplified as we run Quest Archive Manager which talks to the IS using MAPI in just the same way that he has Blackberries that also talk to the IS (via a BES) via MAPI, so we have a constant conversion cycle going going.
Hi is quite correct in that it isn't related to the volume of email.
We had some small gains by manually aligning storage boundaries however we are planning an Exchnage 2007 migration to alleviate this issue.
However when Disabled Archive Manager for three weeks as an extended test, the difference was phenomenal, after it had finished coverting everything back to the stm for the Entourage users, the Exchange Server was behaving the way a Dual Xeon 3.2 with 4gb memory and Exchnage Databases on a 14x36gb 10k RAID5 array should do (it was flying).
Peter Gilber also believes there is a problem with WebDAV:
I have a client, MS Small Business Server 2003, 7 PCs in the office. I convinced one user to move to a Mac at home (iMac 20" mactel). He loves it. I received an email from his ISP asking what is causing all of this increased traffic? Turned out he leaves Entourage 2004 open all of the time at home and while he does get a lot of email, he doesn't receive many large attachments. Well, after digging through the ISP's logs/reports they sent me -- his Entourage downloaded 5GB during one day. So I can attest to a flawed WebDav implementation here. Let's hope Entourage 2008 utilizes RPC over HTTP like Outlook2003+ does. (Best excuse to use Exchange2003/ Outlook2003/2007). Maybe we Mac users will even get to sync Tasks and Notes too!
Dedrick Allen has 120 Entourage clients but doesn't see a problem:
What Mr. Liebsch describes in his article about Entourage taxing his Exchange server is pretty bizarre. We have Exchange 2003 running on a much less server than he has and we don't have any performance problems.
Our server is a Dual Xeon 3Ghz with 4 GB of RAM. 5 HD's with 4 in a RAID5 (total 250GB) for the OS and database files and a single drive for the transaction logs. 100 Mbit network We run spam filters and antivirus filters on the same server with very minimal taxing of the server.
We have about 120 Entourage users about 230 Outlook and OWA users. Our users have a 512MB mailbox limit. Some have up to 1GB depending on their job. Several use Palm's and several use Blackberry's in addition to their desktops. We also allow them to use POP services to access their mail from other clients in or outside the network. Even with all this traffic, our server is still VERY underutilized. We are also able to perform every 4 hour incremental backups on the Exchange server without slowing down user interaction.
We have NEVER seen a server performance problem. I would suggest he take a look at his IIS configuration and several of the OS config options. WebDAV is served via IIS and if IIS is not configured properly it can cause problems. Also if he has some sort of IIS filtering/preprocessing going on it can interfere. Also, clear all the event logs and reboot the server. Then go back and look for an entry that Exchange says your server is not properly tuned. Exchange 2003 can sometimes detect bad configuration and will report so in the event viewer.
I agree with him however that Entourage is not an ideal Exchange client. I wish MS would have just ported Outlook 2001 for Mac to a native OS X application. It worked much better and had more Exchange specific functionality than Entourage does. Other than the lack of some of the Exchange specific features the only problems we have with Entourage is database corruption when storing the MUD folders in a users network home directory. We moved the MUD folder to the local machine and the problem went away.
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