Cause:
If the second drive is assigned the same unix device name that was assigned to the RAID device before it was dismounted from the system, the second drive will be reformatted.

Solution:
External drives should not be removed or attached during a RAID change operation.

Important: There are many different implementations of RAID. Among the most common are RAID 0, RAID 1, and RAID 5.

RAID 0 uses striping to create a single large-capacity drive with high throughput. RAID 0 is much faster and more efficient than using two separate drives. However, a major disadvantage is that the stripes are not redundant; if one of the drives fails, all of the data will be lost. Therefore, RAID 0 should not be used as "data backup insurance." RAID 0 is all performance and no protection.

RAID 1 is redundant but not striped. The same data is stored on two (or more) different drives. RAID 1 is also called disk mirroring. The data is protected, but performance is much slower with RAID 1.

RAID 5 uses three or more drives (usually between three and five). RAID 5’s redundancy is based not on mirroring but on parity. Parity is a computational method in binary logic that generates a parity value from a set of data. If any one of those data elements is lost, it can be recreated using the remaining data and the parity value, no matter which element is lost. In RAID 5, this means that parity can completely reconstruct one of the drives in the array in the event of a failure.

Notes:

• For support for Samsung hard disk drives set in a RAID array, see the documentation for your PC’s motherboard or your host controller card.
• If you don’t know what motherboard or Serial ATA controller you are using, see the instruction or owners manual for your computer. You can also contact your computer manufacture for support. Not all manufactures are listed here, the tables below offer a list of the most common manufactures. If your manufacture is not listed here perform a Google search for their support site.

RAID Hardware is always a disk controller to which you can cable up the disk drives. RAID Software is a set of kernel modules coupled together with management utilities that implement RAID in Software and require no additional hardware.

Pros and cons

Software RAID is more flexible than Hardware RAID. Software RAID is also considerably less expensive. On the other hand, a Software RAID system requires more CPU cycles and power to run well than a comparable Hardware RAID System. Also, because Software RAID operates on a partition by partition basis where a number of individual disk partitions are grouped together as opposed to Hardware RAID systems which generally group together entire disk drives, Software RAID tends be slightly more complicated to run. This is because it has more available configurations and options. An added benefit to the slightly more expensive Hardware RAID solution is that many Hardware RAID systems incorporate features that are specialized for optimizing the performance of your system. For more detailed information on the differences between Software RAID and Hardware RAID you may want to visit: www.adaptec.com

Assess the needs of your system and then decide which RAID solution works best for you. Please do keep in mind however, that regardless of which RAID solution you choose, neither can provide against administrator (human) error. Therefore, frequent, regularly scheduled back ups of your system are highly recommended.

Highlights

• User-configurable RAID solution
• Use RAID 0 for high performance disk striping or RAID 1 for automatic mirroring
• Up to 1 TB storage capacity
• FireWire® 800 for fast data transfer
• Oxford 924 chipset
• Pre-formatted for Mac; easily formatted for Windows®
• Available in RAID 0 only, and RAID 0 / RAID 1 (user configurable) configurations.

What does this mean?

Maxtor OneTouch III Turbo drives are shipped with 2 drives inside the enclosure. These drives are configured in such a way that the drive letter or volume spans both drives to make one large drive. This is known as RAID 0 or RAID Striping.

When data is written to this large volume, the data is "striped" across the two drives.  The stripe size is 64 KB. What this means is that a file written to the array is split into two parts, one for each drive. This translates into significant improvement in reads and writes because two drives can do the work of one in roughtly half the time. This usually means throughput of 30-40% higher than a single drive, and sometimes can be nearly 50% higher.

The file splitting is automatically handled by the operating system so it makes it a simple and robust solution for adding speedy storage or backup.

RAID is an acronym which stands for "Redundant Array of Independent (or Inexpensive) Disks" which is not entirely accurate for the way RAID 0 is used because there is no redundancy. A RAID 0 volume needs to be backed up but is extremely fast.

The following illustration shows how data is arranged on the two drives in RAID 0 and RAID 1:

RAID 0/1 drives support both modes, requiring a reformat to switch the mode. The RAID 0/1 version of the OneTouch III Turbo is expected to ship within a few weeks of the RAID 0 model.

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.

If you install and use a desktop edition hard drive connected to a RAID controller, the drive may not work correctly unless jointly qualified by an enterprise OEM. This is caused by the normal error recovery procedure that a desktop edition hard drive uses.

When an error is found on a desktop edition hard drive, the drive will enter into a deep recovery cycle to attempt to repair the error, recover the data from the problematic area, and then reallocate a dedicated area to replace the problematic area. This process can take up to 2 minutes depending on the severity of the issue. Most RAID controllers allow a very short amount of time for a hard drive to recover from an error. If a hard drive takes too long to complete this process, the drive will be dropped from the RAID array. Most RAID controllers allow from 7 to 15 seconds for error recovery before dropping a hard drive from an array. Western Digital does not recommend installing desktop edition hard drives in an enterprise environment (on a RAID controller).

Western Digital RAID edition hard drives have a feature called TLER (Time Limited Error Recovery) which stops the hard drive from entering into a deep recovery cycle. The hard drive will only spend 7 seconds to attempt to recover. This means that the hard drive will not be dropped from a RAID array. Though TLER is designed for RAID environments, it is fully compatible and will not be detrimental when used in non-RAID environments.

Qty of 2 – 1TB internal hard drives:
• Spanning – 2TB
• RAID-0 – 2TB
• RAID-1 – 1TB
• RAID-5 – Not Supported

Qty of 3 – 1TB internal hard drives:
• Spanning – 3TB
• RAID-0 – 3TB
• RAID-1 – Not Supported
• RAID-5 – 2TB

Qty of 4 – 1TB internal hard drives:
• Spanning – 4TB
• RAID-0 – 4TB
• RAID-1 – Not Supported
• RAID-5 – 3TB

For more support information about the available RAID modes on the WD ShareSpace, please see the chart below:

Cause:
The cause of this issue is unknown.

 Resolution:
To resolve this issue, please connect the My Book Studio II via USB or 1394b (FireWire800) and perform the RAID change again.

1. With the computer powered off, follow the instructions for installing the RAID controller correctly and connect both Serial ATA hard drives to the controller.
2. Boot your computer with the controller and drives already installed.
3. Watch your boot screens for a prompt that will ask you to press the Control and F keys at the same time to enter the Fastbuild utility and press those keys to enter.
4. Press the 1 key to enter Auto Setup.
5. Verify that the top of the screen says Optimize Array for: Security.
6. If the top of the screen says Performance instead of Security, highlight the word Performance and press the right arrow button to change the word to Security.
7. Press the Control and Y keys at the same time to save the array configuration.
8. Press the Y key to create and quick initialize the array.
9. You will be warned that all data on the drives will be erased, press the Y key to proceed.
10. The array is now created, press any key to reboot.

To use the array for extra data storage only:

• Install the latest service pack for your operating system to enable large drive support and use Disk Management to partition and format the array.

To use the array as your bootable system drive:

• Set your BIOS to boot to CD first and boot from your Windows 2000/XP CD to load your operating system onto the array.
• Windows will treat the array as one large drive and will install on the array just as it would on a single drive.
• When you are prompted by Windows setup to press the F6 key to install SCSI or RAID drivers, you will need to press F6 and insert the driver disk that came with your RAID controller.
• Once the drivers for the controller are installed you will be able to finish the installation of Windows 2000/XP onto the array. After the installation of Windows, please install the latest service pack for Windows to enable large drive support and avoid data corruption.

Note: Your system BIOS may require you to change the order of your boot sequence before you can boot your computer from a controller. For more information about adjusting options in your system BIOS, please contact the manufacturer of your computer or motherboard.

RAID is an acronym for Redundant Array of independent Disks. With RAID enabled on a storage system you can connect two or more drives in the system so that they act like one big fast drive or set them up so that one drive in the system is used to automatically and instantaneously duplicate (or mirror) your data for real-time backup.

There are three reasons you might want a RAID system of drives.

1. You need tons of storage space and you need it to be fast. (RAID 0)
2. You want to instantaneously and automatically backup your data. (RAID 1)
3. You want both. (RAID 5)

Which RAID mode should i use?

1. Speed (RAID 0)

Set in high-performance mode (also called striped mode or RAID 0) the storage system gives you the power you need when you’re:

• Designing huge graphics and need a lightning-fast photoshop scratch space.
• Recording large DV files while maintaining clean audio performance.
• Editing DV or HD video and want a smooth work flow with no dropped frames.
• Rendering complex 3D objects or special effects.
• performing disk-intensive database operations.
• Driven to be the first geek on your block with a computer so fast it blows your socks off.

Why is RAID 0 so fast? it’s a bit complicated, but suffice it to say that two or more heads, or in this case, drives, are better than one. picture multiple hoses filling a bucket at the same time or several men bailing a boat and you can understand why two drives striped are faster than one. Data is saved (striped) across both drives and accessed in parallel by all the drives so you get higher data transfer rates on large data accesses and higher input/output rates on small data accesses.

2. Data protection (RAID 1)

Set the system to data protection mode (also known as mirrored mode or RAID 1) and the capacity is divided in half. Half of the capacity is used to store your data and half is used for a duplicate copy.

Why do i want that kind of redundancy? it’s your data, your family pictures, your movie of baby’s first steps, your first novel. is it important? You decide. if it is, then RAID mirroring is for you.

3. Data protection and speed (RAID 5)

in systems with three or more drives (like 4 TB WD ShareSpace™ Network Storage System) we recommend that you set the system to RAID 5. This gives you the best of both worlds: fast performance by striping data across all drives; data protection by dedicating a quarter of each drive to fault tolerance leaving three quarters of the system capacity available for data storage.

About Spanning (Linear)

Spanning, which is not a RAID mode, combines all the drives in a system into one big volume so they act like one giant drive.  The drives are filled up one drive at a time.  The advantage of using this mode is that you can add more drives without having to reformat the system.