The most common application of DRAM, the first dimension, in most hardware architectures is inside the host system as main memory. Main memory offers very fast access and very high bandwidth for all data that is located there. However, this memory is completely volatile. If the host system experiences power loss or must be rebooted for any reason, all data in main memory will be lost and must be recreated. Because of volatility, main memory is used only for storing data being read and for write buffers waiting to be flushed to disk.
Primary uses are buffers, global cache, named cache, and operating system management.
A higher performance system configuration may have 1 4GB of DRAM configured in main memory. Performance is based upon the ability of the algorithms to keep the data of interest in the cache area so it does not have to be retrieved from magnetic disk drives. Typical disk controller cache sizes run from a single MB on a stand alone disk drive, up to 256MB on open-systems RAID arrays, and as much as 4GB on mainframe storage systems. This system design is referred to as having two dimensions. 2D systems are simple to design, easy to understand, and straight-forward to implement.