This was a question asked by a community college customer deploying Office 365 for Education near Seattle.
Dirsync server syncs AD user objects, groups, contacts to Office 365. User objects are synced as MSO IDs and all mail enabled objects are synced to Exchange Online.
What server hardware do I need for Dirsync?
Sizing your Dirsync server is based on number of objects in your Active Directory. Here is a matrix from the deployment guide:
It also has to be hosted on a 32-bit Windows Server for now. Future Dirsync for Office 365 is more than likely slated for 64-bit. Update 11-28-11: 64-bit Dirsync version available here for download.
Can I run this on a virtual server?
Yes, Dirsync is supported on a virtual server.
How can I prepare my AD Forest prior to setting up Dirsync?
Run the Office 365 readiness tool to analyze your AD Forest and remediate any objects the tool identifies prior to running Dirsync. This will save you a lot of headaches to run this tool first. Grab the tool here.
Do I setup Dirsync first or ADFS (SSO) first?
Setup ADFS and federation first and then setup Dirsync. Logically you would think it would be the other way around however this is the order of operations.
What if I have more than 300,000 Active Directory objects to sync to the cloud?
If you have more than 300,000 (it used to be 20,000 object limit) Active Directory objects you need to open a ticket with support before you enable Dirsync. Additionally, your AD user object size will determine which type of tenant you will be hosted on so you need to be sure you are provisioned on the correct tenant prior to enabling Dirsync as well. Check with support to ensure you are on the correct tenant when going beyond 300,000 AD user objects.
To determine the total amount of AD objects you can run the Office 365 readiness tool to get a ballpark count of objects. Grab the tool here.
How do I size the SQL database for Dirsync?
If you have more than 50,000 AD objects to dirsync it is recommended to move to full blown SQL Server 2008 to handle the database size. If you have less than 50,000 AD objects, you can continue to use the default SQL Server 2008 Express database.
Can I run Dirsync on the same server as ADFS 2.0 server?
No, it is not recommended to run them on the same hardware.
Do I need to make Dirsync server highly available?
No, if your Dirsync server fails you will not be out of commission nor will objects get deleted. You can stand up a new Dirsync server and the objects will get into sync again.
How often does it Dirsync sync with Office 365? Can I force dirsync?
It syncs by default every 3 hours or you can manually force a dirsync process via PowerShell with ‘Start-OnlineCoexistenceSync’ cmdlet. See a reference in Greg’s Dirsync step by step below.
Is there a good place to read about deploying Dirsync server?