SSD vs HDD vs RAID: storage devices on the A+ Core 1 exam

Where storage sits on the 220-1201 exam

Storage devices are objective 3.4, Compare and contrast storage devices, inside Domain 3.0 Hardware. Hardware is 25 percent of the CompTIA A+ Core 1 (220-1201) exam, so this material earns real points.

The phrase compare and contrast in the objective tells you how the questions read. Instead of a build-it scenario, you get asked to tell drive types apart, match a drive to the right interface, or choose the RAID level that fits a requirement, sometimes as a drag-and-drop or performance-based question. Storage also comes back in Domain 5.0, Hardware and Network Troubleshooting, whenever a scenario describes a failing, slow, or noisy drive. This post walks the whole objective in plain English: hard drives, solid-state drives, the interfaces and form factors that trip people up, and the RAID levels. When you want the source of truth, read the 220-1201 exam objectives published by CompTIA.

How does a hard drive work, and which specs matter?

A hard disk drive (HDD) stores data magnetically on spinning platters that a read/write head floats just above. Because it has moving parts, its performance is tied to how fast those platters spin, measured as the spindle speed in revolutions per minute (rpm).

The exam expects the common values, so commit them to memory. Consumer drives usually spin at 5,400 rpm or 7,200 rpm. Higher-performance and enterprise drives reach 10,000 rpm or 15,000 rpm, which lowers access time but runs hotter, louder, and draws more power. Physically, hard drives come in two form factors you have to recognize: 3.5-inch drives, used in desktops and servers where capacity and cost per terabyte win, and 2.5-inch drives, used in laptops and many hot-swap server bays.

Because they are mechanical and cheap per gigabyte, HDDs still earn their place for bulk storage, backups, archives, and video surveillance, anywhere you want a lot of room without paying solid-state prices. The trade is speed and durability: spinning platters are slower than flash and more vulnerable to a bump or a drop. It is the same Domain 3.0 install-and-configure mindset you use when matching the right RAM to a board, match the part to the job in front of you.

SSD vs HDD: what makes a solid-state drive faster?

A solid-state drive (SSD) has no moving parts. It stores data in flash memory, so nothing spins up and no head has to seek, which is why it beats a hard drive on speed, durability, noise, and power draw.

Where SSDs differ from each other is the interface, and that is where points are won or lost. A SATA SSD uses the same SATA connection as a hard drive, so it is capped at SATA III, 6 Gb/s (roughly 600 MB/s once you account for encoding overhead). An NVMe SSD talks over PCIe lanes instead, which removes that ceiling and runs several times faster, and newer PCIe generations keep pushing it higher. The objective also lists SAS (Serial Attached SCSI), a faster serial interface common in servers.

That NVMe ceiling keeps rising because each PCIe generation roughly doubles the bandwidth available per lane. A typical NVMe SSD runs on four lanes (x4), so the generation of the slot largely sets the speed. On PCIe 3.0 a four-lane drive tops out around 3,500 MB/s in sequential reads, PCIe 4.0 roughly doubles that to about 7,000 MB/s, and PCIe 5.0 doubles it again to near 14,000 MB/s. You will not be asked to recite those numbers, but the exam does expect you to know that not all NVMe is equal: a Gen 3 drive and a Gen 5 drive can both read NVMe on the label and still be worlds apart. Slots stay compatible across generations, so a newer drive works in an older slot, it just runs at the slower generation's speed.

Form factors matter just as much. A 2.5-inch SSD drops into a standard drive bay and looks almost identical to a 2.5-inch hard drive. An M.2 SSD is a small bare circuit board, most often the 2280 size, which is 22 mm wide and 80 mm long. The older mSATA form factor is legacy now and largely replaced by M.2. Here is the trap the exam loves: M.2 is only a shape. A single M.2 slot can carry a SATA signal or a PCIe/NVMe signal, so a drive that fits physically will not always deliver the speed you assumed.

When does an SSD, an HDD, or both make the most sense?

There is rarely one right drive, and the exam wants the reasoning, not a favorite. Use an SSD where speed is actually felt: the operating system, installed applications, and the files you open constantly. Reach for NVMe specifically when the workload is heavy on input and output, like video editing or running virtual machines. Use an HDD when you need a lot of cheap capacity you touch rarely, such as backups, archives, and large media libraries.

That is why so many real desktops ship with both, a smaller SSD as the boot drive and a large hard drive for storage. Reliability cuts both ways, and the exam knows it. An SSD has no moving parts to wear out mechanically, but its flash cells have a finite number of writes. A hard drive can run for years, yet its motor and heads are physical parts that eventually fail, often with warning noises first. Neither one replaces a real backup. The same objective also touches removable storage like flash drives and memory cards, plus optical drives, so do not forget those exist. This is the kind of compare-and-contrast call worth drilling until it is automatic, which is exactly what Study mode is built for.

Spotting a dying drive is part of the same objective and it resurfaces in troubleshooting scenarios, so learn the warning signs. Both drive types report their own health through SMART (Self-Monitoring, Analysis, and Reporting Technology), readable with the built-in tools or a free utility. On a hard drive, a rising reallocated sector count is an early red flag, and audible clicking or grinding usually means the heads or motor are on their way out. An SSD gives you no sound to go on, so SMART is how you see it coming: because flash wears out by writes, drives publish a rated endurance in terabytes written (TBW) and a remaining-life percentage that counts down as that budget is spent. And to close the loop with the RAID section, none of this is a substitute for backup. A perfectly healthy drive, a mirror, and a full parity array all still lose your data to an accidental delete, ransomware, or a stolen laptop. Only a separate copy protects against those.

Which RAID levels does the A+ exam test?

The 220-1201 objective names five RAID levels: 0, 1, 5, 6, and 10. For each one, know what it does for performance, what it does for fault tolerance, and the minimum number of drives it needs. Those three facts answer almost every RAID question you will see.

One rule ties it all together: RAID is about uptime, not backup. A mirror faithfully copies a ransomware encryption or an accidental delete to every drive in the set, so you still need real backups running alongside any array.

• RAID 0 (striping): splits data across drives for speed and uses the full combined capacity, but adds no redundancy. Minimum 2 drives. If any single drive fails, the entire array is lost.
• RAID 1 (mirroring): writes identical copies to two drives. Minimum 2 drives. It survives one drive failing, and you keep about half of the raw capacity.
• RAID 5 (striping with distributed parity): spreads data and parity across all drives. Minimum 3 drives. It survives one drive failure and rebuilds the missing data from parity, at the cost of one drive's worth of capacity.
• RAID 6 (striping with dual parity): like RAID 5 with a second, independent parity block. Minimum 4 drives. It survives two drives failing at once, at the cost of two drives' worth of capacity.
• RAID 10 (a mirror of stripes, written 1+0): combines mirroring and striping for both speed and redundancy. Minimum 4 drives. It survives at least one drive failure, and more as long as no single mirrored pair loses both of its members.

The one-page version of A+ storage

Storage on CompTIA A+ Core 1 is objective 3.4, and it rewards clean definitions. A hard drive is mechanical: know the spindle speeds (5,400 / 7,200 / 10,000 / 15,000 rpm) and the 3.5-inch and 2.5-inch form factors. An SSD is flash: SATA tops out at 6 Gb/s while NVMe rides PCIe for much more, doubling roughly with each PCIe generation, and M.2 is only a shape, so always confirm the interface a slot supports. For RAID, memorize the minimum drives and fault tolerance for 0, 1, 5, 6, and 10, and remember that an array is uptime, not a backup. Learn why each choice gets made, not just the numbers, and you will handle both the exam questions and the real bench work behind them. When you are ready for the scenarios where a drive is the suspect, walk through the A+ seven-step troubleshooting method and put it to work.