CompTIA A+ Hardware Summary

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.

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.

In each row, three blocks hold data and one holds parity. Parity takes up the space of one whole disk.

1. Number of disks: 4
2. Disks' worth of space used for parity: 1
3. 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.

An SSD stores data on flash memory chips instead of spinning platters and a moving read/write head. With no moving parts, it reads and writes much faster, uses less power, and handles bumps better than an HDD.

Wrong choices

• It keeps data only while the power is on: That describes RAM. Both SSDs and HDDs keep data when the power is off.
• It needs to be defragmented every week: SSDs do not need regular defragmenting. Their speed does not depend on where data sits.
• It always costs less per gigabyte: SSDs usually cost more per gigabyte than HDDs, especially at large sizes.

RAM (random access memory) is the computer's short-term working space. It is very fast, but it is volatile, which means it is cleared when the power goes off. Files that must be kept are saved to storage such as an SSD or HDD.

Wrong choices

• Firmware (BIOS/UEFI) chip: The firmware chip keeps its contents without power so the computer can start.
• Hard disk drive: A hard disk drive stores data long term on spinning platters and keeps it without power.
• SSD: An SSD stores data long term and keeps it when the power is off.

In a laser printer, the fuser uses heat and pressure to melt the toner and bond it to the paper. If the fuser is failing or not hot enough, the toner sits loose on the page and smears or rubs off.

Wrong choices

• Paper pickup roller: A worn pickup roller causes paper jams or failed feeding, not smeared toner.
• Imaging drum: A damaged drum usually causes marks or lines that repeat down the page, not toner that rubs off.
• Toner cartridge low on toner: Low toner makes prints faded or light. The toner that is printed still sticks to the page.

HDMI carries digital video and audio on one cable, which is why it is common on TVs, monitors, and PCs. VGA is an older analog video-only connector.

Wrong choices

• VGA: VGA carries analog video only. It does not carry audio.
• SATA: SATA connects storage drives inside a computer, not displays.
• RJ45: RJ45 is the connector on network cables. It does not carry video to a TV.

A TPM (Trusted Platform Module) is a security chip on or built into the motherboard. It stores encryption keys safely and checks that the startup process has not been changed. BitLocker uses it, and Windows 11 requires TPM 2.0.

Wrong choices

• GPU: The GPU draws graphics on the screen. It does not hold encryption keys.
• NVMe drive: An NVMe drive stores files. The keys that protect an encrypted drive are kept in the TPM, not on the drive itself.
• CMOS battery: The CMOS battery keeps the clock and firmware settings when the PC is unplugged. It does not store encryption keys.

Thermal paste fills the tiny gaps between the CPU and the cooler's base so heat can flow into the heatsink. Without it, the air gaps trap heat and the CPU overheats even though the fan is spinning.

Wrong choices

• Updating the chipset driver: A chipset driver does not move heat away from the CPU. The overheating started right after the cooler was installed.
• Installing a higher-wattage power supply: A bigger power supply does not help the cooler carry heat away from the CPU.
• Installing more RAM: Adding memory does not cool the CPU.

NVMe SSDs talk to the computer over the PCIe bus, which is much faster than SATA. Many M.2 slots support both SATA and NVMe drives, and NVMe is the faster choice.

Wrong choices

• A 7,200 RPM hard disk drive: A hard disk drive uses spinning platters, is much slower than any SSD, and does not fit an M.2 slot.
• A SATA M.2 SSD: A SATA SSD fits the M.2 slot, but it is limited by the slower SATA interface.
• A USB 2.0 flash drive: USB 2.0 is very slow and does not plug into an M.2 slot.