RAID Configuration for Database Server Requirements

SK0-005 By islever Editorial Last updated

Short answer

C OS - Two SSD RAID 1 -

Question

An engineer is configuring the RAID on a new server that will support a large database handling real-time data processing. The system needs to have the largest available space with the best write performance. Given the following disks and configurations: • Four 300GB SSD disks • Eight 1.2TB 15K SAS disks • Must include redundant OS disk Which of the following configurations would meet all the necessary requirements for the new database server?
  1. OS-Two SSD RAID 1 -
  2. OS - One SSD RAID 0 -
  3. OS - Two SSD RAID 1 - Correct Answer
  4. OS - Two SSD RAID 0 -

Key Takeaways

The exam tests the trade-off between raw write performance (RAID 0) and fault tolerance/redundancy requirements, specifically identifying that 'redundant OS disk' mandates at least RAID 1 or 10, eliminating RAID 0 options.

This question tests the ability to balance storage capacity, performance, and redundancy for a database server using SSDs and SAS disks. The community consensus favors RAID 1 for the OS and RAID 5 for the data to maximize available space while maintaining necessary redundancy.

Common mistake: Option A is the most common wrong answer; candidates choose it because they prioritize the 'best write performance' of RAID 5 over the 'largest available space' requirement, or they misunderstand the capacity difference between RAID 5 with all active disks versus configurations with hot spares.

Expert Analysis

Why the Answer Is Correct

Option C is correct because it satisfies the strict requirement for a redundant OS disk by using two SSDs in RAID 1. For the data volume, using eight 1.2TB SAS disks in RAID 5 provides the largest usable capacity among valid redundant configurations (7/8ths of total raw space). While RAID 10 offers better write performance, it only utilizes half the raw space (4/8ths), violating the 'largest available space' constraint.

Why the Other Options Are Wrong

Options B and D use RAID 0 for the OS, which provides zero redundancy, directly contradicting the 'Must include redundant OS disk' requirement. Option A uses two SSDs for the OS (correct redundancy) but implies a configuration for the data that results in less usable space than Option C, likely due to the inclusion of hot spares or a different RAID level interpretation that reduces active disk count.

Community Comment Notes

Comment [1] highlights that Option C is chosen specifically because it delivers more capacity than Option A. Comment [3] notes that while having no hot spares is suboptimal for maintenance, keeping all 8 disks active maximizes storage capacity compared to sacrificing disks for spares.

Exam Strategy

Always check for mandatory constraints like 'redundant OS' first to eliminate invalid options immediately. When balancing 'largest space' vs. 'performance,' calculate the usable capacity (parity overhead) for each valid redundant RAID level to ensure you meet the primary sizing requirement.

Community Votes

C
67%
A
33%

67% of anonymous learners picked answer C. Votes are pick records left by other test-takers — they are not the verified answer.

Discussion 3 contributions

Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.

From public community threads 3

  1. fluke92 👍 1 Answered A
    Why the Other Options Are Incorrect: B. OS - One SSD RAID 0, DB Logs - One SSD RAID 0, Data - Eight 1.2TB 15K SAS RAID 6: RAID 0 offers no redundancy for the OS or DB logs, which violates the requirement for redundant OS disks. RAID 6 provides high redundancy (tolerates two disk failures), but it sacrifices write performance, which is not ideal for real-time data processing. C. OS - Two SSD RAID 1, DB Logs - Two SSD RAID 1, Data - Eight 1.2TB 15K SAS RAID 5, No hot-spare disks: While this setup meets most requirements, the absence of hot spares leaves the system vulnerable during rebuilds after a drive failure, reducing overall reliability. D. OS - Two SSD RAID 0, DB Logs - Two SSD RAID 1, Data - Eight 1.2TB 15K SAS RAID 5, No hot-spare disks: RAID 0 for the OS provides no redundancy, which is unacceptable for critical systems. Additionally, the absence of hot spares weakens fault tolerance.
  2. SecNoob27639 👍 1 Answered C
    C. Personal feelings aside (and mentioned later) it's the most capacity and provides OS redundancy. I absolutely abhor this answer, because the big thing with RAID 5 is hot swappable redundant disks, and not having any spare disks is borderline painful, but having all 8 disks active means you have more storage than having 6 of the disks active and 2 spares. In an ideal world, C would be 7 active and 1 spare drive, but that's not what it is. Given RAID 5 loses the equivalent of 1 complete disk to parity information, the difference is 7TB with 2.4 sitting on the shelf, or 9.4TB with nothing sitting on the shelf for when a drive fails. It goes against every best practice I have ever run up against, but C is technically the most correct answer, even if it's not "best practice."
  3. Stache 👍 1 Answered C
    Going with (C) * Only reason it isn't A is because question asked for "the most available space" which C delivers.

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