1. Deduplication is not enabled by default. You must enable it and manually configure it in Server Roles | File And Storage Services | File and iSCSI Services. Once enabled, it also needs to be configured on a volume-by-volume basis.
2. Content is only deduplicated after n number of days, with n being 5 by default, but this is user-configurable.
3. Deduplication can be constrained by directory or file type. If you want to exclude certain kinds of files or folders from deduplication, you can specify those as well.
4. The deduplication process is self-throttling and can be run at varying priority levels. You can set the actual deduplication process to run at low priority and it will pause itself if the system is under heavy load. You can also set a window of time for the deduplicator to run at full speed, during off-hours, for example.
5. All of the deduplication information about a given volume is kept on that volume, so it can be moved without injury to another system that supports deduplication. If you move it to a system that doesn't have deduplication, you'll only be able to see the nondeduplicated files. The best rule is not to move a deduplicated volume unless it's to another Windows Server 2012 machine.
6. If you have a branch server also running deduplication, it shares data about deduped files with the central server and thus cuts down on the amount of data needed to be sent between the two.
7. Backing up deduplicated volumes :
A block based backup solution or a disk image backup method should work as it will preserve all deduplication data.
File-based backups will also work, but they won't preserve deduplication data unless they're dedupe-aware. They'll back up everything in its original, discrete, undeduplicated form. What's more, this means backup media should be large enough to hold the undeduplicated data as well.
The native Windows Server Backup solution is dedupe-aware.
8. The type of data that is being deduplicated plays a major factor in whether it will be better to use native deduplication or backup software deduplication. There are restrictions on the type of data that you can deduplicate using Windows server 2012. The reason for this is that backup software does not usually alter the original data. Instead, it focuses on removing redundancy before the data is sent to the backup server.
Windows Server 2012's deduplication does alter the original data. That being the case, there are some types of data that are poor candidates for deduplication. Specifically, Microsoft recommends that you do not deduplicate Hyper-V hosts, Exchange Servers, SQL Servers, WSUS servers or volumes containing files that are 1 TB in size or larger. The essence of this recommendation is that volumes containing large amounts of locked data (such as a database) or rapidly changing data tend not to be good for deduplication.
