Exchange 2010 High CPU usage

Question

I have an issue with a recently migrated SBS 2011 server. All appears to be running fine but I noticed it running slow and saw that it was running at 100% CPU. Taking a look, it's mainly two services using it all up:

Store.exe and MSExchangeMailboxAssistant.exe

Both are fluctuating constantly between 20-50% CPU. I have just rebooted the server and it's still behaving like this. I've tried stopping and restarting services etc with no luck at all.

The server has 16Gb of RAM and about 90gb of free hd space. Before the reboot store.exe was using just under 8gb of RAM, which is as expected, and total ram usage was around 80% - as expected.

The Server sits at a client with about 15 users. Mailboxes for 10 of these people are capped at 2Gb. Several users do have very large mailboxes (10gb) due to a large number of CAD files, plans, drawings etc.

Any ideas on what could be causing the high CPU usage?

Four things come to mind when store.exe is seeing high usage.

1. Third-party applications on the Exchange server. It could be anti-virus (that's usually the case) that checks the mailbox database. Perhaps some form of special indexing or archiving tool. If you have non of those, move on.
2. The Exchange server itself has a virus. This happens sometimes. Sad, but true. To me, it seems that SBS machines are more prone to this, not because of anything about SBS itself, but more because of the culture surrounding the small deployment scenarious that SBS usually fits in.
3. The mailbox databases are experiencing some form of corruption that isn't enough to take the database offline completely. You need to research the "Information Store Integrity Checker (ISinteg)". If you have SP1 of Exchange 2010, ISinteg is no longer a standalone app, but has been turned into the followin two PowerShell / EMS cmdlets: New-MailboxRepairRequest and New-PublicFolderDatabaseRepairRequest
4. The Exchange server needs to be updated. I know, this one is kinda lame. However, plenty of update rollups, hotfixes and patches have been released that address spiking store.exe issues. Make double sure that you have all pertinent patches. Double check WSUS or whatever you use to manage patches. Make sure everything is approved and then wait to make sure that wuau.exe presents the updates to the SBS machine itself.

Comments

[MrGigu]

Welcome to SBS 2011, perhaps the biggest memory hog I've ever seen (but if you have enough RAM to throw at the problem, it's worth it; 16Gb should be fine). How recent is this migration?

[Wesley]

@vlannoob Indeed, evaluating and applying a queue of patches is one of the first things that I do when troubleshooting large systems like Exchange. It may be that as you look at the available patches, one of the symptoms that one of the patches addresses is what you're experiencing.

[Jack Morrison]

Mailbox repair seemed to fix the issue - cheers for all answers guys ;)