Computer storage is the component that keeps your operating system, apps, and files when the power is off. The two main types are solid-state drives (SSDs), which use flash memory, and hard disk drives (HDDs), which use spinning disks. How a drive connects, through SATA or NVMe, and its physical form, such as M.2, determine how fast it is and which computers it fits.
Storage Essentials at a Glance
SSDs are much faster, quieter, and more durable than HDDs
HDDs offer more capacity for the money, which suits backups and media libraries
NVMe SSDs connect through PCIe and are much faster than SATA drives
M.2 is a small card-shaped form factor that can use either NVMe or SATA
Storage capacity is measured in gigabytes (GB) and terabytes (TB)
SSD vs. HDD
How an SSD works
A solid-state drive stores data on NAND flash memory chips, with a controller that manages where data is written and read. With no moving parts, an SSD can reach any file almost instantly, which makes startup, app loading, and file transfers much faster.
How an HDD works
A hard disk drive stores data magnetically on spinning platters. A read/write head on a moving arm finds the data, so the drive takes longer to reach files scattered across the disk. Desktop HDDs commonly spin at 5,400 or 7,200 revolutions per minute (RPM), and faster spinning generally means faster access.
Solid-state drive (SSD) | Hard disk drive (HDD) | |
Technology | Flash memory, no moving parts | Spinning magnetic platters |
Speed | Much faster startup, app loading, and file access | Slower, especially with many small files |
Durability | More resistant to bumps and drops | Moving parts are more sensitive to shock |
Noise | Silent | Audible spinning and clicking |
Cost per GB | Higher | Lower |
Best for | Operating system, apps, games, and active projects | Backups, archives, and large media libraries |
For most computers, an SSD is the best choice for the main drive. Many desktops pair an SSD with a large HDD for extra capacity. Learn more about desktop memory and storage.
SATA vs. NVMe
The interface is how a drive talks to the rest of the computer, and it has a big effect on speed.
SATA drives
Serial Advanced Technology Attachment (SATA) is an older interface originally designed for hard drives. SATA SSDs are much faster than HDDs, but the interface tops out at roughly 550 to 600 megabytes per second (MB/s). SATA drives connect with a data cable and a power cable, or plug into an M.2 slot that supports SATA.
NVMe drives
Non-Volatile Memory Express (NVMe) is a protocol built for flash storage. NVMe SSDs connect through Peripheral Component Interconnect Express (PCIe) lanes, the same high-speed paths used by graphics cards, so they're many times faster than SATA.
PCIe generations for NVMe SSDs
Interface | Approximate top sequential read speed |
SATA III | Up to about 550 MB/s |
PCIe 3.0 NVMe | Up to about 3,500 MB/s |
PCIe 4.0 NVMe | Up to about 7,000 MB/s |
PCIe 5.0 NVMe | More than 10,000 MB/s on fast drives |
These are top speeds for fast drives; real-world speeds depend on the drive, the task, and the computer. Each PCIe generation is backward compatible, so a newer drive works in an older slot at the older slot's speed. For everyday use, the jump from an HDD to any SSD is far more noticeable than the jump between PCIe generations. Learn more about ports and interfaces and PCIe slots.
Storage Form Factors
Form factor is a drive's physical size and shape. It decides where the drive fits, while the interface decides how fast it runs.
Form factor | Typical interface | Where it's used |
M.2 | NVMe or SATA | Most modern laptops and desktops |
2.5-inch | SATA | Older laptops and desktop drive bays |
3.5-inch | SATA | Desktop HDDs for high capacity |
M.2 sizes and keys
M.2 drives are small circuit boards that plug directly into the motherboard. Their size is listed as a four-digit number giving width and length in millimeters: M.2 2280 is 22 mm wide and 80 mm long, the most common size, while smaller 2230 and 2242 drives fit compact laptops and devices. The notches on the connector, called keys, show what the slot supports. Most NVMe SSDs use an M key.
An M.2 slot can support NVMe, SATA, or both, so check your computer's specifications before buying a drive. Learn more about motherboards.
Other types of storage
Embedded storage: Some budget laptops and tablets use flash storage built onto the motherboard, which is usually slower than an NVMe SSD and can't be upgraded.
External drives: Portable SSDs and HDDs connect over USB or Thunderbolt for backups and extra space. Learn more about external storage.
Cloud storage: Online services store files on remote servers you can reach from any device. Learn more about cloud software.
Storage Capacity
Storage capacity is measured in gigabytes (GB) and terabytes (TB), where 1TB equals 1,000GB. Your computer may show slightly less usable space than the drive's labeled size, because the operating system measures capacity differently and some space is used by system files.
How you use your computer | Recommended storage |
Browsing and documents, with files in the cloud | 256GB to 512GB SSD |
Everyday home, school, and office use | 512GB SSD |
Gaming | 1TB SSD or more |
Photo and video editing | 1TB SSD or more, plus extra drives |
Large media libraries and backups | An SSD plus a high-capacity HDD or external drive |
SSD Endurance
Flash memory can handle a limited number of write cycles. Manufacturers rate SSD endurance in terabytes written (TBW), the total amount of data a drive is designed to write over its life. For everyday use, modern SSDs typically outlast the computer they're in. Endurance matters more for heavy, constant writing, such as video editing workstations and servers.
How to Choose Storage
Use an SSD as your main drive: It makes the biggest difference in everyday speed.
Check what your computer supports: Look at the M.2 slot size, whether it supports NVMe or SATA, and the PCIe generation.
Pick a capacity with room to grow: Leave space for apps, updates, and files you'll add over time.
Add an HDD or external drive for bulk storage: Use them for backups and large media libraries.
Back up important files: Keep copies on an external drive or in the cloud in case a drive fails.
For upgrade steps, see our guide to desktop upgrades.
Frequently Asked Questions About Storage
Is NVMe the same as M.2?
NVMe and M.2 aren't the same. M.2 is a physical form factor, the shape and size of the drive, while NVMe is the protocol a drive uses to communicate over PCIe. An M.2 drive can use either NVMe or SATA, and NVMe drives are much faster.
Is an SSD worth it over an HDD?
An SSD is worth it for the main drive in almost any computer, because it makes startup, app loading, and file access much faster. An HDD still makes sense as a second drive for large, low-cost storage.
Can you put an NVMe SSD in any M.2 slot?
An NVMe SSD works only in M.2 slots that support NVMe. Some M.2 slots support only SATA drives, so check the computer's specifications or motherboard manual before buying.
How long do SSDs last?
Modern SSDs typically last for many years of normal use, often longer than the computer itself. Their endurance is rated in terabytes written (TBW), which matters most for workloads that write large amounts of data every day.
Related Components Topics
Computer components: the main parts of a computer and how they work together
Memory (RAM): RAM types, speed, capacity, and dual channel
Motherboards: chipsets, sockets, form factors, and expansion slots
Ports and interfaces: USB, Thunderbolt, and PCIe
