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 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.

Yes, you can the NAS 4000 Series for JBOD (just a bunch of disks), spanned, spanned and mirrored, or striped disk configurations.

Please Note:   Depending on how the WD ShareSpace RAID is setup, that RAID array may not be recoverable from a drive failure.

Qty of 2 – 1TB internal hard drives:

• RAID-0 – 2TB – (Not recoverable)
• RAID-1 – 1TB – (Recoverable)
• RAID-5 – (Not Supported)

Qty of 3 – 1TB internal hard drives:

• Spanning – 3TB – (Non recoverable)
• RAID-0 – 3TB – (Non recoverable)
• RAID-1 – (Not Supported)
• RAID-5 – 2TB – (Recoverable)

Qty of 4 – 1TB internal hard drives:

• Spanning – 4TB – (Non recoverable)
• RAID-0 – 4TB – (Non recoverable)
• RAID-1 (Double Mirror) – (Recoverable)
• RAID-5 – 3TB – (Recoverable)

For a recoverable RAID mode:
To recover the ShareSpace from Drive failure, or from a degraded RAID array, you must replace the failed drive with a Western Digital unformatted drive of the same model and size. Once the drive is replaced, the ShareSpace will re-sync the drive back into the RAID array and automatically start the RAID re-build. No further user intervention is needed, other than replacing the failed drive in the unit.

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.

• Identify a failed RAID 5 Volume
• Remove/Replace a Failed Drive in a Failed RAID 5 Volume
• Recover a RAID 5 Volume

…using Seagate’s BlackArmor Manager?

Seagate BlackArmor NAS 440 products come with a RAID 5 Volume by default to ensure data protection. If one drive fails, a user can:

• Easily identify the failed drive using the BlackArmor Manager and other tools.
• Remove the defective drive and replace it with a functioning drive provided by Seagate.
• Use BlackArmor Manager to claim the replacement drive and recover the RAID 5 volume.

All of these things can be accomplished while the BlackArmor NAS 440 is still running.

Procedure(s):
Part 1 – Identifying a Drive failure:
The following options are available for identifying drive failures.

• Web Events in BlackArmor Manager – if a drive fails or if a RAID is running in a degraded state, a Web Event will occur. A Web Event is shown via an amber bar with a warning message within it. The bar will be located at the top of the BlackArmor Manager pages (no matter which one) in your browser. After reviewing the event message, you can click the Acknowledge button to remove it.
• LCD Screen will display a message that denote a drive failure.
• Email notifications – If email setup is enabled through BlackArmor Manager. Users with their email address included in the Email Setup page.
• BlackArmor Manager’s Storage -> Disk Manager can also identify if a drive is failed. It will do so with messaging under a drive’s status.

Seagate Video Tutorial – Identifying a Drive Failure

Part 2 –Drive Removal/Replacement:
Follow these steps to remove and replace a hard drive.
NOTE: Only Seagate hard drives can be used for replacement. Failure to use Seagate replacement parts can and will forfeit the warranty period of the BlackArmor NAS 440/420.

WARNING – PLEASE READ
ESD precautions
Electrostatic discharge (ESD) can damage the processor, hard drives, main board, memory modules (RAM), and other BlackArmor components. Always observe the following precautions before replacing a hard drive:

• Do not remove a component from its protective packaging until you are ready to install it.
• Do not touch the component pins, leads, or circuitry.
• Wear a wrist grounding strap and attach it to a metal part of the computer before handling components. If a wrist strap is not available, maintain contact with the computer throughout any procedure requiring ESD protection.
• Keep the work area free of nonconductive materials, such as ordinary plastic assembly aids and foam packing.

Removing a Hard Drive

1. Open the BlackArmor Manager web interface.
2. In the menu bar, select Storage.
3. Select Disk Manager.
4. Beside the failed disk drive, click the Safe to Remove icon, and then click OK.
5. Open the front panel of the server.
6. Locate the failed hard drive. Ensure that there is no activity on the drive by checking its LED—it should not be illuminated.
   WARNING: Never remove more than one (1) drive at a time. Removing more than one drive will result in data loss.
7. Press down on the orange button to release the drive from the server. If the server is powered on, wait until the drive stops spinning (approximately one minute) before continuing.
8. Holding the handle, gently slide the hard drive partially out of the server until you can get a firm grip on the drive itself.
   Caution: Because the hard drive is heavy, do not completely remove it or carry it by the plastic handle. Hold the drive firmly on the top and bottom.
9. Position (hold) the hard drive/carrier so that the drive label is facing up and the connectors are facing you.
10. Carefully bend the right side of the plastic carrier outward to release the failed drive from the carrier.
11. Remove the failed hard from the plastic carrier enclosure.

Inserting a New Hard Drive

1. Insert the new hard drive so that it fits completely and snugly into the carrier.
2. Carefully slide the new drive into the server. Push firmly to install it completely, and then close the handle to lock the drive into place.
   The hard drive’s LED should turn green.
3. Close the front panel of the server.

Seagate Interactive Tutorial – Hard Drive Replacement

Step 3 – Drive Removal/Replacement:
The following provides the steps necessary for using Seagate’s BlackArmor Manager to claim a replacement drive and recover a RAID 5 volume.
Note: It is assumed that you are logged into the BlackArmor Manager as an admin user before proceeding.

Claiming the New HDD:

1. Mouseover Storage and click the Disk Manager link. The Disk Manager page opens.
2. Locate the replacement hard drive from the list provided (it should be listed as Foreign) and click on the Claim Disk icon. A window opens, asking you to confirm this request.
3. Click the OK button. The drive reclamation starts processing. When finished, the Disk Manager displays a text message stating that, "HDD (hard disk drive)…claimed successfully". The disk is ready to be recovered into a volume.

Recovering the degraded RAID 5 Volume:

1. Mouseover Storage and click the Volumes link. The Volumes page opens.
2. Click the Recover icon. A Volumes page opens showing the Volume Name to be recovered and the Disk Selection (HDD Number).
3. Click the Submit button. A window opens asking you to confirm this request.
4. Click the OK button. The recovery starts processing. When finished, the Volumes page displays a text message stating "RAID configuration changed successfully – resynching/formatting".

Note: Recovery may require a long time. Average recovery times vary from 4 – 12 hours, depending on the size of the volume. When finished the "RAID configuration…" message disappears.
The RAID 5 volume is recovered.

Seagate Interactive Tutorial – Recovering the RAID 5 Volume

• You have backed up any/all critical data off of the BlackArmor NAS Server.
• All previous unneeded volumes have been deleted.
• You are currently logged into the BlackArmor Manager with admin privileges.

Procedure(s):

1. Mouseover Storage and click Volumes. The Volumes page opens.
2. Click the Add icon. The Volume Add Disk Selection page opens. Select the drives (HDDs) you wish to include in the volume.
3. Click Next. The Volume Add RAID Type page opens. Click on the RAID 5 radio button.
4. Click Next. Enter the following information:
   1. Volume Name
   2. Volume Description
   3. Check whether to Encrypt the volume.
   4. Enter a Volume Size or check the Max box to use the entire space of the selected drives.
5. Click Next. The Volume Add Summary page opens, showing you the settings for the volume.
6. Click Finish. Volume creation starts processing. When finished, the volume prepares. This may take awhile depending on the size of the volume. When finished, the message "RAID configuration changed successfully…" disappears, the volume is ready for use.

Seagate Video Tutorial – Creating a RAID 5 Volume

Yes, you can the NAS 4000 Series for JBOD (just a bunch of disks), spanned, spanned and mirrored, or striped disk configurations.