--- description: "SSD reference guide: interfaces from SATA to PCIe Gen6, NAND types, controllers, consumer vs enterprise, and how we test." title: SSD Reference Guide image: https://www.storagereview.com/wp-content/uploads/2025/05/StorageReviewSquare.webp --- [![Storage Review]()](https://storagereview.com/) --- [Facebook](https://www.facebook.com/@storagereview) [X (Twitter)](https://twitter.twitter.com/storagereview) [Instagram](https://www.instagram.com/storagereview/) [LinkedIn](https://www.linkedin.com/company/storagereview-com) [YouTube](https://www.youtube.com/user/storagereview?sub_confirmation=1) [Email](mailto:info@storagereview.com) [Spotify](https://open.spotify.com/show/1y6VnznABhHeOSMOmbDTz0) [Reddit](https://www.reddit.com/r/StorageReview/) [Discord](https://discord.gg/TwMHb4azdC) [RSS Feed](https://www.storagereview.com/rss.xml) [TikTok](https://www.tiktok.com/@storagereview) [Facebook](https://www.facebook.com/@storagereview) [X (Twitter)](https://twitter.com/storagereview) [Instagram](https://www.instagram.com/storagereview/) [LinkedIn](https://www.linkedin.com/company/storagereview-com) [YouTube](https://www.youtube.com/user/storagereview?sub_confirmation=1) [Email](mailto:info@storagereview.com) [Spotify](https://open.spotify.com/show/1y6VnznABhHeOSMOmbDTz0) [Reddit](https://www.reddit.com/r/StorageReview/) [Discord](https://discord.gg/TwMHb4azdC) [RSS Feed](https://www.storagereview.com/rss.xml) [TikTok](https://www.tiktok.com/@storagereview) [![StorageReview.com](https://www.storagereview.com/wp-content/uploads/2026/07/Storage-Review-2x.png)](https://www.storagereview.com) ≡ Menu - [Home](https://www.storagereview.com/) - [Storage Reviews](https://www.storagereview.com/review) - [End User Reviews](https://www.storagereview.com/consumer) - [Enterprise Reviews](https://www.storagereview.com/enterprise) - [Ubiquiti Reviews](https://www.storagereview.com/best/ubiquiti-reviews) - [SR Merch](https://store.storagereview.com) - [Leaderboards](https://www.storagereview.com/best) - [Best Storage Arrays](https://www.storagereview.com/best/storage-arrays) - [Best Enterprise SSDs](https://www.storagereview.com/best/enterprise-ssds) - [Best Servers](https://www.storagereview.com/best/servers) - [Best Enterprise GPUs](https://www.storagereview.com/best/enterprise-gpus) - [Best Desktops for Local AI](https://www.storagereview.com/best/desktops-local-ai) - [Best Laptops for Local AI](https://www.storagereview.com/best/laptops-local-ai) - [Best Local LLM Tools](https://www.storagereview.com/best/local-llm-tools) - [Agentic AI Hardware](https://www.storagereview.com/best/agentic-ai-hardware) - [Best SSDs & Hard Drives](https://www.storagereview.com/best_drives) - [Best Portable SSDs](https://www.storagereview.com/best/portable-ssds) - [Best Business Laptops](https://www.storagereview.com/best/business-laptops) - [Best Mobile Workstations](https://www.storagereview.com/best/mobile-workstations) - [Best Desktop Workstations](https://www.storagereview.com/best/desktop-workstations) - [Best Mini PCs](https://www.storagereview.com/best/mini-pcs) - [Best Laptop Battery Life](https://www.storagereview.com/best/laptop-battery-life) - [Storage Reference Guide](https://www.storagereview.com/storage-reference-guide) - [About SR](https://www.storagereview.com/about-storagereview) - [StorageReview.com Sweepstakes Rules and Regulations](https://www.storagereview.com/storagereview-com-sweepstakes-rules-and-regulations) Search [Home](https://www.storagereview.com/) » SSD Reference Guide # SSD Reference Guide Solid-state drives are the default storage for nearly every computer sold today and the performance tier of every datacenter. This guide is the starting point for understanding how SSDs work, what separates one from another, and which reviews to read when it is time to buy. Every recommendation on this page traces back to testing in the StorageReview lab; for current picks by category, start with our [Leaderboard](https://www.storagereview.com/best_drives). ## What is an SSD? An SSD stores data in NAND flash memory with no moving parts, which is why it beats a hard drive on latency by a factor of hundreds and survives being dropped. A controller chip manages where data lands on the flash, wear leveling, error correction, and the interface to the host. For the full explainer, see [What is an SSD?](https://www.storagereview.com/what-is-an-ssd-solid-state-drive), and for the honest comparison against spinning disks, [SSD vs HDD](https://www.storagereview.com/ssd-vs-hdd). ## Interfaces and form factors Consumer SSDs today are overwhelmingly M.2 sticks speaking NVMe over PCIe. Gen4 drives are the value tier, Gen5 is the performance mainstream at up to roughly 15GB/s in our testing, and PCIe Gen6 has arrived in the enterprise, with [Gen6 drives now in mass production](https://www.storagereview.com/news/samsung-pm1763-pcie-gen6-ssd-enters-mass-production-with-28-4-gb-s-reads) at 28GB/s and up. SATA remains for legacy upgrades but has been performance-obsolete for a decade. In the datacenter, 2.5-inch U.2/U.3 is giving way to the EDSFF family, with E3.S emerging as the standard slot in AI and storage servers and E1.S in dense compute. ## NAND flash types NAND is defined by bits per cell: SLC (one), MLC (two), TLC (three), and QLC (four). More bits per cell means more capacity per dollar and less endurance and speed, which controllers offset with pseudo-SLC caching and increasingly capable error correction. TLC is today’s mainstream for both consumer and enterprise performance drives, while QLC owns the capacity tier, reaching [122TB](https://www.storagereview.com/review/solidigm-122-88tb-d5-p5336-review-high-capacity-storage-meets-operational-efficiency) and even [245TB in a single drive](https://www.storagereview.com/review/micron-6600-ion-245tb-ssd-review-a-quarter-petabyte-per-drive-bay). Modern NAND stacks well past 200 layers, and the roadmap keeps climbing. ## Controllers, DRAM, and caching The controller is where SSDs differentiate. It maps logical addresses to physical flash, spreads writes for endurance, and manages the pseudo-SLC cache that gives consumer drives their burst speed. Drives with onboard DRAM hold that map in fast memory; DRAM-less designs borrow host memory (HMB) and save cost, a fine trade in the value tier. Sustained-write behavior after the cache fills is where cheap and premium drives part ways, which is why our reviews test past the cache. The [SanDisk WD\_BLACK SN8100](https://www.storagereview.com/review/sandisk-wd_black-sn8100-review-elite-performance-in-a-gen5-ssd) is the current reference point for what a well-tuned Gen5 controller delivers, including the power efficiency early Gen5 drives lacked. ## Consumer vs enterprise SSDs Consumer drives optimize for burst performance, price, and efficiency. Enterprise drives optimize for sustained, mixed workloads, consistent latency, power-loss protection, and endurance measured in drive writes per day. The categories genuinely differ: a drive like the [Micron 9550 MAX](https://www.storagereview.com/review/micron-9550-max-review-balanced-performance-for-ai-db-and-analytics) is engineered for AI, database, and analytics duty cycles no consumer drive should see, while read-intensive datacenter drives like the [KIOXIA CD9P-R](https://www.storagereview.com/review/kioxia-cd9p-r-review-read-intensive-gen5-up-to-61-44tb) trade write endurance for capacity and efficiency. ## How we test Consumer drives face real applications and traces: game load, content creation, LLM model loading, PCMark, 3DMark Storage, and sustained transfer testing beyond the cache. Enterprise drives run FIO synthetic workloads plus application and AI pipelines in our lab servers. The methodology behind every chart lives in each review, so results are comparable across drives and generations. ## Where to go next For definitions of every term you will hit in a spec sheet, the [SSD Glossary](https://www.storagereview.com/ssd-glossary) covers the vocabulary. For buying decisions, the [Leaderboard](https://www.storagereview.com/best_drives) holds our current picks across consumer, enterprise, and hard drives, updated as new reviews publish. 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