After participating in the Hosted Exchange 2010 SP1 TAP we now have a solid grasp of some of the more important advances in the product that are of significant benefit to hosting partners. These are primarily support for native multi-tenancy provisioning and performance improvements.
Exchange 2010 SP1 Hosting (I add Hosting on the end to differentiate from the standard enterprise version) introduces a new multi-tenant model with accompanying PowerShell Cmdlets. In this new design each specific Exchange Object (such as an Address List) associated with an organization is stored in its own Configuration Unit within the Configuration Container is Active Directory. So address lists, for example, are clearly tied to an organization and isolated. There is no need for the extra security settings and complex pointers that we used in HMC to associate Exchange Objects with a tenant organization. User objects are then stored in a tenant specific OU. This is what makes the product "natively" multi-tenant and is an example of why the previous Hosted Messaging and Collaboration (HMC) provisioning engine was no longer needed for Exchange 2010 SP1 Hosting.
Another significant benefit is that the provisioning performance is much faster than with HMC, and also more efficient in terms of the amount of code needed to leverage the Cmdlets. This allows a lot of flexibility for ISVs to create solutions on top of this, especially filling the various gaps left from HMC, such as a reseller model and providing an API for Control Panels to leverage.
I consider it important to have this native multi-tenancy design and automation provided in the product so that it will be supported by Microsoft and also provide a predictable provisioning experience on Exchange 2010 regardless of what Control Panel a hosting partner maybe using. As a Systems Integrator, knowing what we’re getting into and having a consistent experience for provisioning across all our clients is an important benefit. It also opens the possibility that other products such as SharePoint 2010 and Systems Center Operations Manager may be able to leverage this tenant model so that we have one tenant model across the Microsoft hosting platform.
Now on to performance improvements. Firstly, there is about a 70% reduction in Input/Output Operations per Second (IOPS). This is important because historically with Exchange the only way to get acceptable levels of IOPS was to use many disks in a RAID stripe set, usually only possible with an expensive SAN. This then opens the possibility of getting adequate performance using single inexpensive Direct Attached Storage disk drives and replicating the databases to other mailbox servers to get fault tolerance. This storage approach is nicknamed JBOD – “Just a Bunch of Disks”. There is a nice summary here: http://blogs.technet.com/b/ucedsg/archive/2009/05/11/what-is-new-with-exchange-2010-storage.aspx
In summary, the native multi-tenancy provisioning and performance improvements are a very significant advancement in Hosted Exchange, developed by the Exchange Product group in a single version of Exchange, and supported by Microsoft. These are some good foundations for hosting partners to move forward with as they plan for their next generation platform.