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Solid-state drive

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A solid-state drive, or SSD, is a high-performance storage device. It uses integrated circuits to store data persistently. This means the information stays safe even when the power is turned off. These devices are also called semiconductor storage devices or solid-state disks. SSDs are essential for modern technology because they provide fast data access. They are found in personal computers, mobile devices, and massive enterprise servers.

Samsung SSD 840 120GB MZ-7TD120--4 LID REMOVED
Samsung SSD 840 120GB MZ-7TD120--4 LID REMOVED

Most SSDs function using a type of non-volatile memory called NAND flash. This memory stores data within tiny components called memory cells. The performance and endurance of the drive depend on how many bits are stored in each cell. Single-level cells, or SLC, store only one bit per cell. This design makes them very fast and durable. In contrast, multi-level cells (MLC), triple-level cells (TLC), and quad-level cells (QLC) store more bits per cell. While these allow for more storage, they generally have lower performance and endurance.

M.2 2242 SSD connected into USB 3.0 adapter
M.2 2242 SSD connected into USB 3.0 adapter

Some advanced drives use different mechanisms to achieve even higher speeds. For example, 3D XPoint technology, used in Intel's Optane, offers faster speeds and higher endurance. Instead of storing electrical charges in cells like NAND flash, 3D XPoint changes electrical resistance to store data. This method allows for faster data access and longer persistence. Furthermore, SSDs use internal parallelism to manage multiple operations at once. This ability to handle many tasks simultaneously greatly enhances their overall performance.

128GB 2230 NVME SSD
128GB 2230 NVME SSD

SSDs differ significantly from traditional hard disk drives (HDDs) because they have no moving parts. HDDs are electromechanical devices that use spinning magnetic disks and moving heads to find data. Because SSDs are entirely electronic, they offer much lower latency and higher input/output rates (IOPS). They are also much more rugged and resistant to physical shock. Additionally, SSDs operate silently and consume much less power. High-performance SSDs use only about one-third to one-half of the power required by HDDs.

480 GB OCZ-AGIL ITY3
480 GB OCZ-AGIL ITY3

There are many ways to connect an SSD to a computer system. Older interfaces like SATA and SAS allow them to act as direct replacements for HDDs. Newer, faster interfaces include NVM Express (NVMe) over PCI Express (PCIe). There are also many different physical shapes, called form factors. These include mSATA, M.2, U.2, and the EDSFF. Some hybrid solutions, known as solid-state hybrid drives (SSHDs), combine SSD and HDD technologies. Examples include Intel's Hystor and Apple's Fusion Drive, which use flash memory to speed up frequently accessed data.

Viper PVP30 Portable SSD 2 TB-3001
Viper PVP30 Portable SSD 2 TB-3001

While SSDs are very reliable, they do have specific limitations. Every SSD has a finite number of write cycles, meaning the cells eventually wear out. To manage this, controllers use complex wear-leveling algorithms to spread data across the drive. If an SSD reaches its maximum terabytes written (TBW), it may lose data more quickly. For instance, a 1 TB Samsung 970 EVO has an endurance rating of 600 TBW. Additionally, NAND flash can slowly leak charge when unpowered. A consumer drive might lose data after one to two years if left unpowered in storage.

Historical cost of computer memory and storage
Historical cost of computer memory and storage

Comparing costs and capacities shows why HDDs are still used for some tasks. As of late 2025, SSDs cost roughly $0.05 to $0.10 per gigabyte for large 4TB or 8TB models. HDDs are much cheaper, costing only $0.01 to $0.03 per gigabyte for the same capacity. However, SSDs offer much higher maximum capacities, reaching up to 245.76TB. In terms of speed, consumer SSDs can reach transfer rates between 200 MB/s and 14,800 MB/s. This is vastly superior to the roughly 200 MB/s typical of many HDDs.

MacBook Air Mid 2012
MacBook Air Mid 2012
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🖼️ Images & Media (11)
File:2023 Dysk SSD Patriot P210 2TB.jpg
2023 Dysk SSD Patriot P210 2TB.jpg
File:480 GB OCZ-AGIL ITY3.png
480 GB OCZ-AGIL ITY3.png
File:CompactFlash IDE Adaptor.jpeg
CompactFlash IDE Adaptor.jpeg
File:M.2 2242 SSD connected into USB 3.0 adapter.jpg
M.2 2242 SSD connected into USB 3.0 adapter.jpg
File:Mushkin Ventura USB-SSD.jpg
Mushkin Ventura USB-SSD.jpg
File:Viper PVP30 Portable SSD 2 TB-3001.jpg
Viper PVP30 Portable SSD 2 TB-3001.jpg
File:Samsung SSD 840 120GB MZ-7TD120--4 LID REMOVED.JPG
Samsung SSD 840 120GB MZ-7TD120--4 LID REMOVED.JPG
File:Disk on module.jpg
Disk on module.jpg
File:128GB 2230 NVME SSD.jpg
128GB 2230 NVME SSD.jpg
File:Historical cost of computer memory and storage.svg
Historical cost of computer memory and storage.svg
File:MacBook Air Mid 2012.png
MacBook Air Mid 2012.png
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