Large Disk I/O for small number of users

Question

Hi Guys,
I'm trying to figure out why my Outlook 2010 Clients are having a bad experience with their connections to the server often timing out.  You know the popup message in the system tray that says "Outlook is trying to communicate with server"
I'm running SBS 2011 with the usual Exchange 2010 underneath.  It was installed last October and has been slowly getting worse over recent months.  All my service packs and updates are applied both on the server and on the workstations.
I have been searching for solutions for a while.  I have run the Exchange BPA and corrected any minor reported problems.
I'm running the server as a VM and nothing seems to be overloaded or poorly configured. The host server has two RAID sets one make up of 10k drives and the other of 15k drives.  The VHD's for the OS are on the 15k drives and the data VHD is on the 10k.
I have upped the virtual RAM on the SBS Server VM to 32GB which is the Maximum.
Task manager reports 4.9GB as being Free and 4.4GB on Standby. So RAM isn't the problem
I the bottleneck appears to be Disk I/O
When I look in the resource monitor I see constant disk I/O around 10-15 MB/s all day.
It does slow down to a couple of MB during the night.
Most of the activity is on the Mailbox.edb and PublicFolder.edb
Currently the public folder has 10mb/s read and 250KB/s write
And the Mailbox folder has 8mb/s read and 10KB/s write
These values are often up and down all over the place but id's say constantly high.
I don't have a lot of users.  Say around 35 active. Some with hand held devices as well.  A few are remote but the majority on the same Gigabit LAN as the server.  Actually I'm at the far end of a 1Mbps connection and have far less
trouble than most.  However I often see my connection silently fail over to https.
I do have a largish public folder database with around 1100 sub folders (all at one level) containing mostly archived emails.
The only other non middle of the road thing we do is with shared calendars.  Multiple users connect to different shared calendars.  Most would only have one or two calenders open at a time but a few users would have 10 or 12 open concurrently.
Any ideas how I can diagnose what is going on with my poor exchange server performance?
Thanks
David

Answer 1

I think I finally found the answer or at least a big part of the cause.
It is Background Virus Scanning.
Every time the virus definitions are updated Exchange / AVG launches a full scan of the entire Mailbox Store and Public Folder Store. This can occur more than once per day during business hours!
I found this link that relates to background virus scanning.
http://technet.microsoft.com/en-us/library/aa998674(v=exchg.80).aspx
The steps to disable background virus scanning from that article are as follows.
Open a registry editor, such as Regedit.exe or Regedt32.exe.
Navigate to:
HKLM\System\CurrentControlSet\Services\MSExchangeIS\VirusScan
In the right-hand pane, double-click the BackgroundScanning value.
In the Value Data field, change the value to 0.
Close the registry editor, and restart the Microsoft Exchange Information Store service, and your antivirus software services for the change to take effect.
There is still lots of disk I/O during the day but this was the cause of the lions share.
Thanks to all those who assisted and I hope this helps someone else.
David (The Dog Master)