The backup device and storage media that you will use in your Server environment is entirely dependent on how much data you need to backup, as well as how often that data is being modified. Things like text documents don't take up very much storage space, whereas images, music, and video files take up an excessive amount of storage space. You will need to determine how much data there is to backup (in MB or GB), as well as how much of that is modified on a weekly and daily basis. This will help you select which backup device you should use:
DVD-RWs: Rewritable DVDs make some of the simplest storage media because of their low cost, reasonably high capacity, and small size. DVD-RWs come in sizes of 4GB and the more expensive dual layer 8GB.
External Hard Drives: External hard drives come in capacities as high as 2TB (2,000GB) and that number is steadily rising, as the price per gig is going down. Although a higher cost than internal hard drives, external HDDs can prove to be a reliable and high capacity storage method. Most enterprises, however, do not prefer external hard drives for a number of reasons, such as physical dimensions, high failure/error rate, and decreased portability.
Tape Drives / Magnetic Tapes: Typically unfamiliar to those who haven't done enterprise level data backups, one of the most common ways of backing up data is with magnetic tapes. Magnetic tapes have a lot of advantages: they're highly portable, fast, durable, and can be rewritten far more times than DVDs. Internal tape drivers, either SAS, SATA, or SCSI attached, are the way to go. The cost of the tape drives, though, is a deterrence to many. They range anywhere from $300 USD to $1500 USD, and that is just for the basic spec. The price variance has to do with the interface, speed, tape size, and number of tapes. Tapes aren't typically that high in capacity - around 40GB - but some tape drives can write to multiples in a backup session. Tapes are recorded linearly, so there is no formatting or file organization to concern yourself with.