Storage Device Facts

What is a hard disk drive (HDD)?

A thick magnetic disk encased in a protective shell with multiple platters and read/write heads for each side.

What are some advantages of HDDs?

Large storage capacity, cheap cost per MB, wide selection.

What are some disadvantages of HDDs?

Prone to failure, vulnerable to physical damage, many are internal devices.

What is SCSI used for?

Transferring data between devices; used with tape drives, hard disks, CD-ROMs, scanners, printers.

What is a solid-state drive (SSD)?

A flash device with no moving parts, used to replace HDDs for OS, apps, and files.

What are some advantages of SSDs?

Faster than HDDs, no moving parts, lower power usage, more durable, smaller/lighter.

What is the main disadvantage of SSDs?

Higher cost compared to HDDs.

What is Non-Volatile Memory Express (NVMe)?

A memory storage device that uses PCIe to access non-volatile memory with low latency and high parallelism.

What are common form factors for NVMe devices?

PCIe expansion cards, 2.5-inch U.2 connector devices, SATA Express, and M.2 devices.

What is flash memory used for?

Storing data in programmable, non-volatile memory (e.g., in cameras, portable devices).

What are some advantages of flash devices?

Reprogrammable, retain content without power, portable, large capacity, inexpensive, fast access.

What are common types of flash memory cards?

CompactFlash, SD, SSD, MiniSD, MicroSD, hybrid cards, memory sticks.

What is an optical disc?

A laser-based storage medium (e.g., CDs, DVDs, Blu-rays) that stores info through pits in a reflective coating.

What are some advantages of optical discs?

Good for media, portable, cheap, long shelf life, recordable, sturdy.

What are some disadvantages of optical discs?

Slower than HDDs, small capacity, compatibility issues.

What is IDE (Integrated Drive Electronics)?

An interface that enables communication between a motherboard’s data bus and hard disks.

Actuator

Controls the movement of the read/write arm in a hard disk drive (HDD).

Actuator arm

Holds the read/write head and moves it across the platters.

Platter

Circular disk inside an HDD that stores data magnetically.

Read/write head

Reads data from and writes data to the platter surfaces.

Spindle

Rotates the platters at high speeds inside an HDD.

HDD RPM (Revolutions Per Minute)

Typical speeds include 5,400, 7,200, and 10,000 RPM; affects data access speed.

Rotational latency

Delay waiting for the disk to spin to the correct position; faster RPM = lower latency.

Number of platters and heads

HDDs may have multiple platters, each with two heads (one per surface).

Drive size comparison

Desktop drives: 3.5"; Laptop drives: 2.5"; SSDs may be 2.5", mSATA, or M.2.

Mini-SATA (mSATA)

Compact SSD form factor using SATA interface; used in small laptops and embedded devices.

M.2 SSD

Small form factor SSD that connects directly to the motherboard; can use SATA or NVMe interface.

AHCI vs NVMe

AHCI: older protocol designed for spinning disks; NVMe: newer, faster protocol for SSDs using PCIe.

NVMe over PCIe

Allows SSDs to bypass AHCI and directly access the CPU over the PCIe bus for higher performance.

M.2 B-Key

Uses up to two PCIe lanes; supports SATA and PCIe x2 devices.

M.2 M-Key

Uses up to four PCIe lanes; supports high-speed NVMe SSDs.

B-Key vs M-Key compatibility

Motherboards must match the key type of the M.2 drive (B, M, or B+M key).

Installing M.2 SSDs

M.2 drives mount directly to the motherboard; require a screw to secure and BIOS support for NVMe.

Flash drive limitations

Flash memory has limited write cycles; unsuitable for constant rewrites or archival storage.

Common flash memory examples

USB drives, SD cards, microSD, SSDs, and embedded storage in mobile devices.

What is the Bernoulli Effect in an HDD?

The cushion of air between the spinning platter and the read/write head that prevents contact while allowing magnetic data access.

How do portable HDDs improve portability?

They connect via USB, allowing easy transfer between systems without internal installation.

What does NVMHCIS stand for?

Non-Volatile Memory Host Controller Interface Specification; another name for the NVMe protocol.

What types of interfaces can M.2 support?

PCI Express 3.0, SATA 3.0, and USB 3.0, with backward compatibility to USB 2.0.

What additional features can M.2 integrate with?

Wi-Fi, Bluetooth, GPS, NFC, digital radio, WiGig, wireless WAN, and other SSDs.

Why are optical discs good for long-term storage?

They are portable, have decent capacity, and are ideal for read-only data backups.

What is a disadvantage of optical discs in terms of durability?

Susceptible to scratches and damage that can make data unreadable.

Why might someone choose a flash drive over an optical disc today?

Flash drives are more durable, compact, and faster with larger storage options.

When should you choose an HDD or SSD over other storage types?

When you need fast access to a large amount of data on a primary system.

When is a flash drive or optical disc more appropriate?

When you need portable storage or to transfer data between systems.

BD-RE

(Blu-ray Disc Rewritable) Standard for Blu-ray discs that allows data to be written, erased, and rewritten multiple times. Ideal for data backup, media storage, and applications requiring frequent updates.

BD-R

A single-use Blu-ray disc that can only be written to once. After the initial write, the data is permanent, similar to a DVD-R or CD-R. Used for archiving large amounts of data, video production, and backup with high storage capacity (up to 25 GB for a single-layer disc and 50 GB for a dual-layer disc).

BD-RW

A Blu-ray disc that can be written to, erased, and rewritten multiple times, similar to a CD-RW or DVD-RW. Ideal for storing data that may need to be updated or erased, useful for frequent backups or video recording.

BD-ROM

A pre-recorded Blu-ray disc that is read-only. Data is permanently written and cannot be altered. Typically used for commercial Blu-ray movies, games, and other pre-packaged content. Cannot be written to or erased.

What do the numbers 32x/12x/48x represent on a CD-RW drive

Read speed is 48x, write speed is 32x, and rewrite speed is 12x. The last number indicates the read speed.

Why is it important to understand CD-RW drive speed ratings?

It helps determine how fast data can be read, written, or rewritten. Important for backups, media creation, and understanding storage device capabilities.