DataArchiva is a Salesforce application available in app exchange and is used Salesforce data archive needs.
DataArchiva is a native to Salesforce platform, which means, the archived data does not leave Salesforce echo system. Being native to Salesforce, there are many advantages w.r.t Security, throughput, platform scalability, hardware, etc.
DataArchiva archives data in to big data storage called Big Objects. DataArchiva has a layer on top of Big Objects that takes care of handling object relationship, data types, indexes, etc under the hood.
No additional software or hardware needed for DataArchiva.
By default Salesforce provides free storage upto 1 million records for Big Objects and beyond this is chargable. The cost of Big Object storage is way cheaper than the regular Salesforce Objects.
This being a big data, large volume of data can be stored in terms of terabytes. There is no official mention of size limit for Big Object from Salesforce.
That's it, nothing else.
Yes, Archival process can be scheduled to run on daily, weekly or monthly basis in background without intervention.
Yes, any standard and custom objects can be archived. In addition, field history, deleted records, audit trail can also be archived.
When your business data grows over time, lots of unused or historical data will occupy storage space. Since storage space is expensive in Salesforce, moving these unused old data to another low cost storage will reduce your storage cost, because these cannot be deleted for audit/analytics reasons.
Backup does not delete source data but rather copies to secondary storage and this will not reduce the Salesforce storage cost. DataArchiva is also capable to work as Backup or in Archive mode.
Yes: Archived data can be pulled using REST/SOAP api.
Since unused/old data is moved to Archive, the application query performance will be improved as it has deal with lesser data.