A company needs to expand their dynamic pool by 10 TB. The current dynamic pool consists of sixty-three 7.6 TB SSD drives that are configured for RAID 5 (12+1). What is the minimum number of drives…

Question

Options

• A2
• B13
• C1
• D15

• A
  5% (1)
• B
  14% (3)
• C
  24% (5)
• D
  57% (12)

Explanation

Option D (15) is correct because expanding a RAID 5 (12+1) dynamic pool requires one complete RAID stripe set of 13 drives (12 data + 1 parity), which yields 12 × 7.6 TB = 91.2 TB of usable capacity - more than enough to satisfy the 10 TB requirement - plus 2 dedicated hot spare drives mandated for pool expansion, giving a minimum of 13 + 2 = 15 drives.

Option B (13) is the most tempting wrong answer: 13 drives do form a complete RAID 5 (12+1) stripe, but the required 2 hot spare drives are omitted, leaving the expanded pool without rebuild protection. Option A (2) fails because 2 drives cannot form a valid RAID 5 (12+1) stripe set at all - you'd have incomplete parity coverage and no usable capacity would be added. Option C (1) is eliminated for the same structural reason: a single drive cannot participate in striped RAID independently.

Memory tip: Think of the formula 12 + 1 + 2 = 15 - 12 data drives, 1 parity drive (completing the stripe), and 2 hot spares. Any time you see "RAID 5 (12+1)" pool expansion on an exam, the base stripe cost is always 13, and enterprise pools require 2 hot spares on top.

No community discussion yet for this question.