CommVault can make implementing archive easy ....
The challenge for most is in the rule creation and end user access. The first requirement is to understand what you have, what is the age of it and the business value. CommVault File Level Analytics (FLA) can provide insight and help you evaluate what you have before and in an ongoing effort to continue providing visibility. Using the FLA reports will give you the insight to help you decide what you want to archive and the rules you want to apply as well as a cost prediction mechanism. When you’re ready to apply the archive rules (age, size, type, location,etc) , start with a less aggressive set of rules and apply more aggressive rules to get to your target. For instance, if you want to have a 90 day archive rule, meaning anything older than 90 days gets archived, start with a 3 year rule and work up to the 90 day rule.
Second, is the end user access. The archive operation has two options when performing the archive, leave a stub behind in the place of the original file or remove the file completely. Leaving a stub allows the end user to recall from the archive by clicking on the stub. You can also elect to enable the end user web console which provides a browse view of the archive. Commonly used more in environments where they don't want to use stubs. An optional search engine can be enabled on the archive data that will give end users full keyword search from the web console. The search index can also be used to enable the Compliance search feature for eDiscovery.
Lastly, a CommVault specific feature can combine the backup, archive and reporting into a single pass, scan and collection utilizing OnePass. OnePass performs a single collection operation that is used for all three use cases. It also simplifies the license model, OnePass is calculated by front end TB's in the current cycle regardless of the implementation of archive or reporting. It can be used to provide all three, without being charged for all three separately. This allows you to license a single collection, apply archive when you’re ready and utilize the FLA to help you along the way.
As to your last question - yes you can backup/archive from a NetApp to an HP storage library and dedupe to tape. Silo is the feature that can dedupe to tape.