How many drives?:

Although two drives are more expensive than a single drive with the same net capacity, two smaller drives are better than one large drive! With multiple drives you simply have more options. The most important of these relates to backups. Since it is unlikely that both drives will fail at the same time, copying the contents of one drive to the other one provides a quick way of making a backup. In addition, with a bit of construction, one can manage to solve the problem of how to run two separate software systems on a single PC.