The Data Server is usually used to performs tasks such as data analysis, storage, data manipulation, archiving, and other non-user specific tasks. This requires a lot of hard disk space. HDD's are usually connected in RAID configuration for maximum data integrity and performance. Hard Drives must be hot-swappable e.g. defective drives should be changed with new ones without the need of system shut down. More RAM and CPU cache is also required.
You can use these servers for SQL databases or as a simple File servers for storing your enterprise data.