The Array and RAID Controller Concept

First let's make sure we know exactly what we're dealing with here. A drive array is a collection of hard disk drives that are grouped together. When we talk about RAID, there is often a distinction between physical drives and arrays and logical drives and arrays. Physical arrays can be divided or grouped together to form one or more logical arrays. These logical arrays can be divided into logical drives that the operating system sees. The logical drives are treated like single hard drives and can be partitioned and formatted accordingly. I know it's confusing but often times most RAID setups are relatively simple. However, they can get complicated when dealing with multiple nested RAID levels in the high-end RAID implementations.

The RAID controller is what manages how the data is stored and accessed across the physical and logical arrays. It ensures that the operating system only sees the logical drives and does not need to worry about managing the underlying schema. As far as the system is concerned, it's dealing with regular hard drives. A RAID controller's functions can be implemented in hardware or software. Hardware implementations are better for RAID levels that require large amounts of calculations. With today's incredibly fast processors, software RAID implementations are more feasible, but the CPU can still get bogged down with large amounts of I/O. Later in the article, I'll discuss which applications and RAID levels are more suited to hardware or software RAID.

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Article Navigation Introduction/What Is RAID? The Array And RAID Controller Concept Mirroring Parity Striping Levels Of RAID Combining Levels Of RAID Benefits Hardware RAID Implemenations Conclusion