Task 4.5: Implementing Disk Fault Tolerance with RAID

A significant aspect of information systems security relates to protecting against the loss of data and ensuring the data’s availability. Data is written on hard disks. These disks can and will fail, resulting in data loss and loss of availability of the data. Fault-tolerant disk arrays are a common approach to mitigating the losses related to disk failure.

Redundant Array of Independent Disks (RAID) systems can be implemented to provide fault tolerance of disks. The two most common implementations of RAID are RAID1 (Mirroring) and RAID5 (Stripe Set With Parity).

RAID1 requires two disks and provides no performance boost or degradation. It provides for one disk to be lost, yet all of the data stored on the mirrored volume remains intact and available. The overhead in disk space for this fault tolerance follows the formula , where n represents the number of disks in the array. In the case of the mirrored volume, two disks are used so the overhead is , or 50 percent.

RAID5 requires three disks minimum and can be extended to 32 disks as a typical maximum. It provides increasing performance boost as the number of disks in the array are utilized. It provides for one disk to be lost, yet all of the data stored on the RAID5 volume remains intact and available. The overhead in disk space for this fault tolerance also follows the formula , where n represents the number of disks in the array. In the case of a 3-disk RAID5 volume, 3 disks are used so the overhead is , or 33 percent. In the case of a 10-disk RAID5 volume, 10 disks are used so the overhead is , or 10 percent. And in the case of a 32-disk RAID5 Volume, 32 disks are used so the overhead is , or 3 percent.

Read and write times in a RAID5 volume follow a similar efficiency. The formula for read and write time performance is t = 1/(n – 1) where n represents the number of disks in the array. As you increase the number of disks in the volume, the performance gets better and better.

Scenario

You are responsible for ensuring the availability of a critical data set on a file server. While the budget is tight, you must implement a fault-tolerant disk array to protect against loss of data and to improve data availability.

Scope of Task

Duration

This task should take 45 minutes.

Setup

Because of budget concerns, you must provide fault tolerance while keeping spending to a minimum. You have chosen to implement Microsoft’s software-based RAID1 to satisfy these issues. You have just added two new disks to your file server.

Caveat

The installation of new hardware and the configuration of partitions or volumes can be risky. Always perform a full backup of the system prior to implementation of any new hardware, software, or changes to the system’s configuration.

Procedure

For this task, you will configure the system with a RAID1 volume to hold your critical data set.

Equipment Used

For this task, you must have:

• Windows Server 2003 system with the following configuration:
  • Two new disks (basic)
• Local Administrator access

Details

New Disk Initialization and Conversion to Dynamic Disk

1. Log on to the Windows Server 2003 system as the Local Administrator with the password Password1.

Fault-tolerant disk arrays are available only on server-class operating systems from Microsoft. You cannot build RAID1 or RAID5 arrays in Windows 2000 Pro, Windows XP, Windows Vista, or Windows 7.

2. Right-click on My Computer and select Manage to open the Computer Management console.

3. In the left pane, select Disk Management. The Initialize And Convert Disk Wizard will launch. Click Next.

4. On the Select Disks To Initialize screen, confirm that the two new disks are selected for initialization. Click Next.

5. On the Select Disks To Convert screen, confirm that the two new disks are selected for conversion to dynamic disks. This is required to assemble a fault-tolerant disk array. Click Next.

6. Confirm that the two new disks are selected for initialization and conversion to dynamic disks. Click Finish.

Creating the RAID1 Mirrored Volume

1. In the Disk Management console, confirm your two new disks are present and are dynamic. Right-click on the Unallocated space on the first new disk and select New Volume.

2. Doing so launches the New Volume Wizard. Click Next.

3. On the Select Volume Type screen, click Mirrored. Then click Next.

4. On the Select Disks screen, select the second new disk on the left side, and then click the Add button. The second disk should appear on the Selected list on the right side, as shown. Click Next.

5. In the Assign Letter Drive Or Path screen, allow the system to assign the next available drive letter. Click Next.

6. On the Format Volume screen, format the volume with NTFS, using the default allocation unit size. Add the volume label MIRROR and select to perform a quick format. Click Next.

7. Confirm the details of the new volume and click Finish.

8. In the Disk Management dialog box, you will observe the new volume is formatting and then resynching.

9. The new volume is complete when you see that it is healthy. Notice in the upper-right corner that the new E: drive, MIRROR, is fault-tolerant.

10. In Explorer, you can copy your critical data to the new, fault-tolerant E: drive.

Criteria for Completion

You have completed this task when you have correctly assembled a fault-tolerant RAID1 volume and can copy data to it.