All the email, calendaring items, contacts, tasks and so forth need to be housed somewhere within Exchange. In the end it all goes into a database and that database needs an engine to help manage it, processes to work with it and additional services to help with the replication of data.
Exchange uses the Extensible Storage Engine (ESE) also known as JET Blue as its database engine and in the end the database is a single .edb file per database (shown in Figure 1). Note: With Exchange 2013 you can have up to 50 mounted databases per Exchange server, which is significantly less than the 100 you could mount with Exchange 2010.
Figure 1: The .edb file with transaction logs
For years folks have been wanting a change to SQL as its database but in the words of Exchange Team expert Ross Smith IV “SQL squeals like a pig where ESE is easy”. My guess is that he means that ESE still outperforms SQL with regard to the type of transactions Exchange requires.
Now in legacy versions of Exchange the information store was a single process (store.exe). With Exchange 2013 the information store has been completely rewritten in C# and renamed the Managed Store. This new store has two processes, the Microsoft.Exchange.Store.Service.exe and the Microsoft.Exchange.Store.Worker.exe process. With each mounted database you have another Microsoft.Exchange.Store.Worker.exe process started up. So, each mount-request will create a new worker process which exits when a database is successfully dismounted. This means that the process of one database does not necessarily impact another process/database when e.g. it hangs.
You can see the worker processes if you take a look at Task Manager on your Exchange server and have multiple databases mounted. Note in Figure 2 that the Store.Service.exe is present and used to help with managing the Store.Worker.exe processes.
Figure 2: Task Manager and the Store.Worker.exe process
This helps isolate single database issues without impacting other active databases running on the same server. Database failover and physical disk handling have been improved, reducing IOPS utilization by + 50% and now supporting disk capacity up to 8TB. ESE has also been enhanced with deeper checkpoint depth for both active and passive database copies.
The new Managed Store is an important new aspect of Exchange 2013 because of the many benefits that we appreciate as a result of the hard work by the Store team. The only negative result (that we may see adjusted by SP1 depending on how important it is in the queue) is with regard to the new 50 mounted databases per Exchange server. Many of you reading this may feel like that isn’t a major concern in your environment and so you have nothing to worry about with migrating toward Exchange 2013.