RAID 1 Explained
The RAID level 1 architecture uses the concept of mirroring. This means that errors and failures of all disks can be accommodated in the disk array, except one. However, there can be maximum two disks only. RAID 1 is designed for faster read operations than write. RAID 1 recovery is only possible when one of the two disks have failed. While using any modern multi-threaded operating system (Windows or Linux), RAID 1 array gives better performance for split seeks, that is, access of same memory location by two different users. There needs to be a RAID 1 controller for each disk in this array for best performance.

RAID 5 Explained
In the architecture of RAID 5 disks, the array is so arranged that failure of one disk can be kept hidden. If the second disk fails before the replacement of the first, then there cannot be any data recovery. The maximum number of disks that can be accommodated in the architecture are three, out of which one is kept as a backup. When the first disk fails, the backup disk springs into action and data recovery is possible. In RAID 5, a failed disk needs to be replaced as early as possible. RAID 5 performance suffers whenever there is a read-modify-write operation.

Recovery in RAID Disks
RAID 5 as well as RAID 1 have one common assumption. Every failure is independent of the other. However, this is not completely true. Due to the mechanical nature of the storage disk, failure of one disk may mechanically be dependent on the other. There are techniques such as, parity resynchronization or stale sub-disk recovery, where recovery is possible but these are restricted to specific scenarios. Data loss due to software reasons (a virus or accidental deletion) is however a different issue. The data recovery techniques used in RAID disks and recovery through data recovery softwares are not directly related.

Advantages of RAID 1

• Redundancy of the data is hundred percent.
• Data need not be rebuilt in case of a single disk failure.
• Even though there are two disks in the array, the rate at which data gets transferred is that of a single disk.
• Very easy to understand and implement.

Advantages of RAID 5

• RAID 5 has an inbuilt load balancing mechanism.
• RAID 5 is ideally suited for database applications which are heavily read oriented.
• Applications that perform random read operations work well on RAID 5.
• High fault tolerance typically requires additional disk space. RAID 5 is highly efficient in that scenario.

The seven levels in RAID have been developed gradually over a period of time. Different arrays are suited for different situations. The above RAID 5 vs RAID 1 comparison may be helpful in understanding these disk array structures.

How do I change the RAID level of a My Book Premium II, My Book Pro II, My Book Studio II, or My Book Mirror Edition external hard drive?

The My Book Premium II, My Book Pro II, and My Book Studio II external hard drives are pre-configured for RAID 0 (Striped) mode for maximum capacity and accelerated performance. These products also support RAID 1 (Mirrored) mode for data protection, which dedicates half the capacity to mirror the data in both internal hard drives.

The My Book Mirror Edition external hard drive is pre-configured for RAID 1 (Mirrored) mode for maximum data protection. This drive also supports RAID 0 (Striped).

These products DO NOT support JBOD or any other RAID configurations. Please follow the directions below to change the RAID level of the My Book Premium II, Pro II, Studio II, or Mirror Edition external hard drive.

Important: Changing the RAID configuration on your My Book external hard drive will erase any existing data currently on the drive. Please ensure that any existing data on the drive is backed up.

Windows:

1. Please ensure that the My Book hard drive is powered on and connected to the computer system. Launch the WD Drive Manager by double-clicking its icon on the desktop or system tray.
2. The external hard drive will be shown in the following screen. Select the external hard drive in the menu and then click on Next.
   
3. Select the desired RAID configuration by clicking on RAID 0 or RAID 1 (the example shown has RAID 1 selected).
4. Ensure that Quick NTFS Format is checked and then click on Next. You can also use Windows Disk Management to repartition and reformat the external hard drive.
   
5. Enter the confirmation number provided on your screen, then click Yes. Click on Yes again to confirm the change.
   
6. Click Close when finished.
   

Macintosh:

1. Please ensure that the My Book external hard drive is powered on and connected to the computer system. To install WD Drive Manager, insert the CD that came with the My Book external hard drive. Double-click the CD-ROM icon, the My Book external hard drive icon, then the Mac folder. Then double-click WD Drive Manager to install this program into the applications folder.
2. The external hard drive will be shown in the following screen.
   
3. Click on the arrows next to the Setup option to change the RAID level. The screen below shows RAID-0 with a format type of HFS+. Click on Configure and then when prompted to confirm, click on Configure again.
   
4. As standard precaution, the system prompts you for an administrator’s name and password to authenticate your action. Enter this information and click OK.
   
5. When configuring the device, My Book RAID Manager will create a a single volume to the format you specified. The new volume will automatically populate to the desktop.