Objective 3.3: Compare and contrast storage devices

Cert: CompTIA A+ Core 1 (220-1201) V15 Domain: 3.0 Hardware Weight: ~25% of Core 1 (domain total; 3.4 is one of eight objectives in this domain) Depth: Compare and contrast. The candidate should look at a scenario and pick the right storage device, interface, form factor, or RAID level. Installation specifics are covered in 3.4.

What this objective tests

You should be able to tell the difference between a hard drive and a solid-state drive, name the common SSD interfaces and form factors, identify the standard RAID levels and what each one trades for what, and know where flash drives, memory cards, and optical drives still fit into real-world IT work.

This is a recognition objective. You're not installing or wiring anything. You're matching the right storage type to the use case.

Key facts

Hard disk drives (HDD):

• Mechanical drives with spinning platters and a moving read/write head. Slower than SSDs but cheaper per gigabyte for large capacities.
• Spindle speeds. The platters spin at a fixed RPM. Common values: 5400 RPM (low power, laptops and external drives), 7200 RPM (desktops and most servers), 10,000 and 15,000 RPM (enterprise, declining as SSDs took over). Faster spindle equals lower seek time and higher throughput.
• Form factors. 2.5-inch (laptops, slim externals, some servers) and 3.5-inch (desktops, full-size servers, NAS). The 2.5-inch is also the standard SSD form factor for SATA SSDs.

Solid-state drives (SSD):

• No moving parts. Flash memory chips on a board. Much faster than HDDs, lower latency, higher random read and write speeds. Cost more per gigabyte but the gap has closed.
• SSDs are categorized by two independent specs: communications interface (how they talk to the system) and physical form factor (what they look like and where they plug in).

SSD communications interfaces:

• SATA (Serial ATA). The same interface used by HDDs. Tops out around 600 MB/s. Easy compatibility, slowest of the SSD interfaces, fine for general-purpose use.
• NVMe (Non-Volatile Memory Express). A protocol designed specifically for flash storage. Runs over PCIe lanes. Many times faster than SATA. Modern laptops and desktops ship with NVMe SSDs by default.
• PCIe (Peripheral Component Interconnect Express). NVMe SSDs use PCIe as their physical bus. You'll see specs like "PCIe Gen 4 x4" describing how many lanes and what generation. Higher generation and more lanes mean more bandwidth.
• SAS (Serial Attached SCSI). Enterprise interface mostly found in servers. Higher reliability, hot-swap support, dual-port redundancy. SAS drives are typically used with hardware RAID controllers in enterprise storage.

SSD form factors:

• 2.5-inch. Looks like a small laptop hard drive. Uses SATA. Fits any 2.5-inch drive bay. Common upgrade path for older laptops and budget desktops.
• M.2. A small stick that plugs directly into the motherboard. Can use SATA or NVMe over PCIe. The motherboard slot must support the interface you have (an NVMe stick will not work in a SATA-only M.2 slot). Common lengths: 2280 (22 mm wide, 80 mm long) is the standard.
• mSATA (Mini-SATA). Older small form factor predecessor to M.2. SATA only. Mostly found in older ultrabooks and some industrial systems. Largely retired but still on the exam.

RAID levels (Redundant Array of Independent Disks):

• RAID is about availability and performance, not backup. A RAID array can be wiped by ransomware, accidental deletion, or controller failure just like any other storage. You still need a separate backup.
• Hardware RAID uses a dedicated controller card. Software RAID is built into the OS (Windows Storage Spaces, Linux mdadm, macOS Disk Utility).

Removable storage:

• Flash drives (USB sticks). USB-connected solid-state storage. Common for file transfer, bootable installation media, and quick portable storage. USB 3.x is significantly faster than USB 2.0; check the port and the drive both support it.
• Memory cards. SD, microSD, CompactFlash, and others. Found in cameras, phones, drones, single-board computers like Raspberry Pi. Different physical sizes and speed classes.

Optical drives:

• CD, DVD, Blu-ray. Most modern desktops and laptops do not ship with optical drives. Still relevant for legacy software installs, audio/video media, and some compliance archive workflows.
• External USB optical drives are the common workaround when a modern machine needs to read an old disc.

Common gotchas

• NVMe in a SATA-only M.2 slot. Some older motherboards have M.2 slots that only support SATA mode. An NVMe stick will fit physically but the system either ignores it or won't boot from it. Always check the motherboard manual for what the M.2 slot supports.
• PCIe lane sharing. Some motherboards share PCIe lanes between the M.2 slot and the primary x16 GPU slot. Installing an NVMe drive can drop the GPU from x16 to x8. Performance hit is usually small but it shows up.
• RAID is not backup. This shows up on the exam and in real life. Candidates and clients both make this mistake. RAID protects against drive failure, not against deletion, corruption, theft, or ransomware.
• Mixing drive sizes in RAID. Most arrays size to the smallest drive, so a 4TB plus 2TB pair in RAID 1 gives you 2TB usable. The extra space on the larger drive is wasted.
• SAS vs SATA. SAS controllers can talk to SATA drives. SATA controllers cannot talk to SAS drives. Trying to put a SAS drive in a SATA-only port will fail.
• 2.5-inch HDD vs 2.5-inch SSD. Same form factor, very different performance and price. A "2.5-inch drive" question on the exam will usually clarify which one, but in real-world purchasing always read the spec sheet.
• Spindle speed confusion. A 7200 RPM HDD is faster than a 5400 RPM HDD, but ANY SSD is dramatically faster than ANY HDD. RPM only matters when comparing HDD to HDD.

Real-world context

Storage is the single biggest perceived-performance upgrade in most environments. An old laptop with a 5400 RPM HDD feels broken; the same laptop with an SSD feels new. This is usually the first hardware recommendation a helpdesk tech makes for a slow machine.

Practical guidance:

• For a basic office laptop or desktop, NVMe SSD is the default in 2026. SATA SSD is still acceptable for budget or older systems. HDD is for archive and bulk storage only.
• For a NAS or file server, large 3.5-inch HDDs in RAID 5 or RAID 6 are still the cost-effective default for bulk capacity. Pair with SSD caching if budget allows.
• For a workstation that needs both speed and capacity, the common setup is a small NVMe SSD for OS and active projects plus a large HDD for archive.
• Flash drives are the helpdesk's swiss army knife: Windows install media, recovery tools, file transfer, BitLocker recovery keys. Keep a labeled set.
• RAID 5 has a known weakness on large modern drives: rebuild times after a failure can take days, and a second drive can fail during the rebuild. RAID 6 or RAID 10 is increasingly the default for drives over 4TB.

Sources

• [CompTIA A+ 220-1201 Exam Objectives Version 4.0, Section 3.4](../../../../../../30-RevyTechJourney/CompTIA%20A%2B%20220-1201%20Exam%20Objectives%20%284.0%29.pdf)
• [Wikipedia: Hard disk drive](https://en.wikipedia.org/wiki/Hard_disk_drive)
• [Wikipedia: Solid-state drive](https://en.wikipedia.org/wiki/Solid-state_drive)
• [Wikipedia: NVM Express](https://en.wikipedia.org/wiki/NVM_Express)
• [Wikipedia: M.2](https://en.wikipedia.org/wiki/M.2)
• [Wikipedia: Serial Attached SCSI](https://en.wikipedia.org/wiki/Serial_Attached_SCSI)
• [Wikipedia: Standard RAID levels](https://en.wikipedia.org/wiki/Standard_RAID_levels)
• [Microsoft Learn: Storage Spaces overview](https://learn.microsoft.com/en-us/windows-server/storage/storage-spaces/overview)