CompTIA Security+ (SY0-701)Security ArchitectureHard
A storage administrator configures a RAID 5 array using five 2TB disks to protect against disk failure while maximizing usable capacity. How much usable storage capacity does this array provide, and how many simultaneous disk failures can it tolerate?
- A10TB usable capacity, tolerates 2 simultaneous disk failures
- B4TB usable capacity, tolerates 1 simultaneous disk failure
- C8TB usable capacity, tolerates 1 simultaneous disk failure
- D6TB usable capacity, tolerates 2 simultaneous disk failures
Show answer & explanationAnswer & explanation
Correct answer: C. 8TB usable capacity, tolerates 1 simultaneous disk failure
RAID 5 uses distributed parity equivalent to one disk's worth of capacity across the array; with five 2TB disks (10TB raw), one disk's capacity (2TB) is used for parity, leaving 8TB usable (4 x 2TB). RAID 5 can tolerate the failure of exactly one disk before data loss occurs, since only a single set of parity data exists.
Why the other options are wrong
- A. Two-disk fault tolerance describes RAID 6, not RAID 5, and this capacity is incorrect.
- B. This capacity assumes two disks are used for parity, which describes RAID 6 math, not RAID 5.
- D. This capacity miscalculates parity overhead and fault tolerance for RAID 5.
RAID 5
A RAID level that stripes data with distributed parity across all disks, tolerating a single disk failure while using the equivalent of one disk's capacity for parity.
- Usable capacity = (n-1) x disk size, where n = number of disks.
- Tolerates exactly 1 simultaneous disk failure.
- RAID 6 adds a second parity set to tolerate 2 disk failures.
Memory trick: RAID 5: lose one disk of space, survive one disk of failure.