A RAID system is a collection of hard drives joined together for speed and fault tolerance.
At least 2 hard drives are required, preferably identical. None of the space is wasted as long as the hard drives used are identical. Data is stored evenly and sequentially across all disks. A striped volume is accessed with a single drive letter as if all the disks were combined in to a single drive. It can be created on FAT, FAT32 and NTFS. This level offers the highest level of performance but no redundancy. If any of the hard drives in the array fails, everything will be lost.
This level is known as mirroring. Two identical copies of data are stored on two drives. When one drive fails, the other drive still has the data to keep the system going. Rebuilding a lost drive is very simple since you still have the second copy. It can be created on FAT, FAT32 and NTFS.
Using an extra RAID controller can increase the fault tolerance even more. Even though the performance benefits are not great, it provides the highest degree of fault tolerance. It is supported only in Windows 2000 Server and Advanced Server .
RAID-5 is identical sized areas of formatted disk space located in 3 or more dynamic disks. Data is stored evenly and sequentially among all disks and parity information is written across all disks in the volume. RAID5 is accessed with a single drive letter as if all the disks were combined in to a single drive. It can be formatted with FAT, FAT32 and NTFS.
If a single disk in the RAID5 fails data can be recovered using the parity information but if more than one disk fails you can not recover data. It is supported only in Windows 2000 Server and Advanced Server