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A network administrator is setting up a web server for a small advertising office and is concerned with data availability. The administrator wishes to implement disk fault tolerance using the minimum number of disks required. Which RAID level should the administrator choose?

A network administrator is setting up a web server for a small advertising office and is concerned with data availability. The administrator wishes to implement disk fault tolerance using the minimum number of disks required. Which RAID level should the administrator choose?

  • RAID 5
  • RAID 0
  • RAID 1
  • RAID 6

The correct answer is: RAID 1.

RAID 1 provides disk fault tolerance using the minimum number of disks required, which is two. It works by mirroring the data across two disks, meaning that an identical copy of the data is stored on each disk. This setup ensures that if one disk fails, the other disk still contains all the data, providing fault tolerance and data availability.

Let’s explore in detail why RAID 1 is the correct answer for the administrator’s needs and how it compares to other RAID levels like RAID 5, RAID 0, and RAID 6.

1. RAID 1 (Correct Answer)

RAID 1, also known as disk mirroring, provides fault tolerance by duplicating data across two disks. This ensures that if one disk fails, the system can continue running using the other disk, which contains an exact copy of the data. RAID 1 requires a minimum of two disks.

Why RAID 1 is Ideal for Disk Fault Tolerance with Minimum Disks:

  • Fault Tolerance: RAID 1 offers excellent fault tolerance because the data is mirrored on two disks. If one disk fails, the other disk continues to operate with no data loss.
  • Minimum of Two Disks: RAID 1 achieves fault tolerance with only two disks, making it the most efficient RAID level in terms of disk usage for redundancy.
  • Simple and Reliable: RAID 1 is simple to implement and very reliable, making it an excellent choice for small businesses or offices where data availability is critical.

Key Benefits of RAID 1:

  • Data Redundancy: Both disks contain identical data, so even in the event of a disk failure, all the data is still available on the other disk.
  • Quick Recovery: If a disk fails, replacing the faulty disk and rebuilding the mirror is straightforward, ensuring minimal downtime.
  • Ease of Implementation: RAID 1 is easy to set up and manage, making it a suitable option for small to medium-sized businesses without complex IT infrastructure.

Use Case:

In this case, the network administrator is setting up a web server for a small office and is concerned with data availability. RAID 1 ensures that the office’s data will be safe and accessible even if one of the disks fails, which is crucial for maintaining server uptime.

2. Why Other RAID Levels Are Less Suitable

RAID 5 (Incorrect)

RAID 5 offers both fault tolerance and increased performance by distributing data and parity (error-correcting information) across three or more disks. If one disk fails, the system can rebuild the missing data using the parity information stored on the remaining disks. However, RAID 5 requires at least three disks.

Why This is Incorrect:

  • Requires More Disks: RAID 5 requires a minimum of three disks to provide fault tolerance. Since the administrator is looking for the solution with the minimum number of disks, RAID 1, which only needs two disks, is a more efficient choice in this case.
  • More Complex Rebuild: While RAID 5 provides fault tolerance, the process of rebuilding the array after a disk failure is more complex and time-consuming than RAID 1.

RAID 0 (Incorrect)

RAID 0 provides no fault tolerance. It uses a technique called striping, which splits data across multiple disks to improve performance, but it does not store any redundant or parity data. If any disk in a RAID 0 array fails, all data in the array is lost.

Why This is Incorrect:

  • No Fault Tolerance: RAID 0 is designed purely for performance by striping data across multiple disks. However, if one disk fails, all the data in the array is lost. Therefore, RAID 0 does not meet the administrator’s requirement for data availability and fault tolerance.

RAID 6 (Incorrect)

RAID 6 is similar to RAID 5 but provides additional fault tolerance by using two sets of parity data, allowing for the failure of up to two disks without data loss. RAID 6 requires a minimum of four disks.

Why This is Incorrect:

  • Requires More Disks: RAID 6 requires at least four disks to provide fault tolerance, which is more than the administrator’s requirement for the minimum number of disks. RAID 1, with just two disks, is more efficient for the given situation.
  • Overhead: RAID 6 has higher overhead due to the need to calculate and store two sets of parity data, which may not be necessary for a small office setting where simple fault tolerance is sufficient.

3. Why RAID 1 is the Best Choice for the Administrator

The key consideration for the network administrator is disk fault tolerance with the minimum number of disks. RAID 1 meets both of these criteria effectively:

  • Fault Tolerance: With RAID 1, if one disk fails, the other disk retains all the data, ensuring no loss of availability.
  • Two Disks Minimum: RAID 1 requires only two disks to provide redundancy, making it the most efficient option in terms of hardware usage for a small office environment.
  • Simple and Reliable: RAID 1 is easy to set up and maintain, providing a straightforward solution for protecting important data on a web server.

Conclusion

The correct answer is RAID 1 because it provides fault tolerance using the minimum number of disks, which is two. This makes it an ideal choice for the network administrator setting up a web server for a small advertising office, where data availability is a concern. Other RAID levels, such as RAID 5 and RAID 6, require more disks to achieve fault tolerance, while RAID 0 provides no fault tolerance at all. RAID 1 offers a balance of simplicity, reliability, and minimal hardware requirements, ensuring that data will be available even if one disk fails.