CompTIA A+: Hardware Concepts
Importance ★★★★★ · 25% (estimate)
Overview
This chapter covers the parts inside and around a computer: cables and connectors, memory, storage, motherboards, CPUs, power supplies, and printers. Many questions ask which part or cable fits a job, or how to set up storage so data is safe.
Memory (RAM) holds data the computer is working on and is cleared when power is off. Desktop memory modules are DIMMs and laptop modules are SO-DIMMs, and the module type must match the motherboard, such as DDR4 or DDR5. Installing matching modules in the right slots lets the board use dual-channel mode for better speed.
Storage keeps data when power is off. Hard disk drives (HDDs) use spinning platters, while solid-state drives (SSDs) have no moving parts and are much faster. NVMe SSDs use the PCIe bus and are faster than SATA SSDs. RAID combines several drives: RAID 0 stripes data for speed with no protection, RAID 1 mirrors two drives, RAID 5 stripes data with parity across at least three drives, RAID 6 uses two parity blocks across at least four drives, and RAID 10 stripes across mirrored pairs and needs at least four drives.
The power supply turns wall AC power into the DC voltages the parts need, and its wattage must cover all the parts. Firmware (BIOS or UEFI) settings control boot order, Secure Boot, the TPM chip, and virtualization support. Laser printers use a fuser to melt toner onto paper, so pages that smear mean the fuser needs attention.
Key concepts
RAID 0
Striping: data is split across two or more drives for speed. There is no redundancy, so one failed drive loses all the data.
Memory tipRAID 0 = zero protection.
RAID 1
Mirroring: the same data is written to two drives. Usable space is one drive's size, and the array survives one drive failure.
Memory tipRAID 1 = a copy on each drive.
RAID 5
Striping with distributed parity across at least 3 drives. Usable space is (number of drives - 1) x drive size. Survives one drive failure.
Memory tipLose one drive's worth of space to parity.
RAID 6 and RAID 10
RAID 6: two parity blocks, at least 4 drives, usable (n - 2) x size, survives two failures. RAID 10: striped mirrors, at least 4 drives, usable space is half.
Memory tipRAID 6 = double parity. RAID 10 = mirrors plus speed.
NVMe
A fast storage interface for SSDs that uses the PCIe bus, often in an M.2 slot.
Memory tipNVMe is faster than SATA.
TPM
Trusted Platform Module: a chip that stores encryption keys safely. BitLocker uses it, and Windows 11 requires TPM 2.0.
Memory tipDrive encryption keys live in the TPM.
Fuser
The laser printer part that uses heat and pressure to bond toner to paper.
Memory tipToner rubs off the page = check the fuser.
See it in a picture
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Often tested
- RAID is not a backup: deleted files and ransomware damage are copied to every drive in the array.
- Usable RAID space: RAID 0 all, RAID 1 half, RAID 5 (n - 1), RAID 6 (n - 2), RAID 10 half.
- Turn on hardware virtualization (Intel VT-x or AMD-V) in firmware before running virtual machines.
- Choose a power supply with enough wattage for every part, plus some extra headroom.
- Apply thermal paste between a CPU and its cooler so heat moves into the heatsink.
Easy to confuse: RAID levels
| Level | Minimum drives | Usable space | Drive failures it survives |
|---|---|---|---|
| RAID 0 | 2 | All | None |
| RAID 1 | 2 | Half | 1 |
| RAID 5 | 3 | (n - 1) x size | 1 |
| RAID 6 | 4 | (n - 2) x size | 2 |
| RAID 10 | 4 | Half | 1 per mirrored pair |
3 sample questions
Verified practice questions from this unit.
Question 1. The figure shows how data and parity blocks are laid out on a disk array. Which RAID level does it show?
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- ① RAID 0
- ② RAID 6
- ③ RAID 10
- ④ RAID 5
▼ Show answer and explanation▲ Hide answer and explanation
Answer: ④ RAID 5
Key point: Striping + one parity block per stripe = RAID 5
Look at each row (stripe). Each one has data blocks spread across the disks plus exactly one parity block, and the parity block moves to a different disk in each row. Striping with distributed parity is RAID 5. If one disk fails, the missing data can be rebuilt from the other blocks and the parity.
Wrong choices
- RAID 0: RAID 0 stripes data with no parity at all. The figure has parity blocks.
- RAID 6: RAID 6 keeps two parity blocks in every stripe. The figure has only one parity block per row.
- RAID 10: RAID 10 keeps identical copies of data on mirrored pairs. The figure has no duplicate blocks, only one parity block per row.
Question 2. A small business has two drives in a server and wants an exact copy of all data on the second drive in case the first one fails. Which RAID level should be used?
- ① RAID 5
- ② RAID 1
- ③ RAID 0
- ④ RAID 10
▼ Show answer and explanation▲ Hide answer and explanation
Answer: ② RAID 1
Key point: RAID 1 = mirroring on two drives
RAID 1 (mirroring) writes the same data to two drives at the same time. If one drive fails, the other still has everything. It needs only two drives, and the usable space equals one drive.
Wrong choices
- RAID 5: RAID 5 also protects data, but it needs at least three drives.
- RAID 0: RAID 0 splits data across drives for speed and keeps no copy. If one drive fails, all data is lost.
- RAID 10: RAID 10 needs at least four drives.
Question 3. The figure shows a disk array. Each disk is 2 TB. How much usable storage space does this array provide?
- ① 4 TB
- ② 2 TB
- ③ 6 TB
- ④ 8 TB
▼ Show answer and explanation▲ Hide answer and explanation
Answer: ③ 6 TB
Key point: RAID 5 usable space = (n - 1) x disk size
In each row, three blocks hold data and one holds parity. Parity takes up the space of one whole disk.
- Number of disks: 4
- Disks' worth of space used for parity: 1
- Usable space = (4 - 1) x 2 TB = 6 TB
Check: 8 TB total - 2 TB for parity = 6 TB.
Wrong choices
- 4 TB: 4 TB would be half the total, which is how mirroring works. This array uses parity, not mirroring.
- 2 TB: 2 TB is the size of one disk. The array stores data on more than one disk.
- 8 TB: 8 TB is the total raw size of all four disks. Part of the space holds parity, so it cannot all be used for data.
AI-written · Verified · Written by AI. Only units that passed a separate AI check (re-reading facts and numbers) are published. Tell us if you find a mistake.