How SSDs Work: NAND Flash Types, 3D Stacking, and Why Prices Keep Falling

SSDs cost 1000× less per gigabyte than they did in 2009 — and understanding why explains both Moore's Law and why the decline will eventually slow

The price per gigabyte of solid-state storage fell from approximately $3.00/GB in 2009 to approximately $0.08/GB for consumer NVMe SSDs in 2024. This 37× price decline in 15 years transformed SSDs from exotic premium products to standard equipment in nearly all new computers. The technology that made this possible — NAND flash memory — has a specific set of characteristics and trade-offs that explain the decline, the current limits, and why SSDs behave differently from HDDs.

How NAND flash works

NAND flash stores data by trapping electrons in a floating gate transistor (or charge-trap structure in newer designs). More electrons = a "1" stored; fewer electrons = a "0" stored.

The "page" and "block" structure:

• Data is written in pages (typically 4KB or 16KB)
• Pages are grouped into blocks (typically 128–512 pages = 512KB–8MB)
• The critical limitation: NAND flash can be written to a page-by-page, but can only be erased at the block level

This asymmetry (write by page, erase by block) is why SSDs can't overwrite data in-place like HDDs. To update a file, the SSD must:

1. Read the entire block containing the target pages
2. Erase the whole block
3. Rewrite all pages, with the updated data in the appropriate pages

This is the "write amplification" problem that affects SSD performance and longevity.

NAND types: the density-reliability trade-off

The flash cells can store different amounts of data depending on how many distinct charge levels are used:

The density breakthrough: QLC packs 4× as much data into the same physical cell area as SLC. This is how the price per gigabyte has fallen — more data per cell means more capacity per wafer, reducing cost.

The reliability trade-off: more charge levels in the same cell means smaller voltage differences between states. Noise and wear cause charge to leak, blurring the distinctions. QLC cells wear out 10× faster than SLC.

3D NAND: the second dimension of density

Original "planar" NAND laid cells flat on a 2D surface. As cell dimensions approached physical limits (around 10–15nm), 3D NAND stacked cell layers vertically.

Layer counts have grown rapidly:

• 2013: first 3D NAND with 24 layers
• 2017: 64-layer 3D NAND (Samsung V-NAND, Micron)
• 2020: 176-layer 3D NAND (Micron)
• 2024: 300+ layer 3D NAND entering production (Samsung, SK Hynix)

More layers = more storage per die = lower cost per gigabyte. The race to add layers is the current primary vector of cost reduction.

NVMe vs SATA: why the interface matters

SATA (Serial ATA): the original SSD interface, adapted from the hard drive era. Maximum speed approximately 600 MB/s (SATA 6Gb/s limit). Every consumer laptop until ~2015 used SATA. Still common in budget systems.

NVMe (Non-Volatile Memory Express): designed specifically for flash storage. Uses the PCIe bus (the same high-speed bus as graphics cards). Sequential read speeds: 3,000–7,000 MB/s for consumer NVMe. Latency also much lower than SATA.

Real-world impact: for most consumer workloads (web browsing, office work, game loading), a SATA SSD already eliminates the HDD bottleneck. NVMe's advantage is most noticeable for:

• Large file transfers (video editing, large backups)
• Game loading (noticeable on next-gen consoles and PC)
• Development workflows with many small file operations

SSD lifespan: the TBW (Terabytes Written) specification

Every SSD specifies a Total Bytes Written (TBW) endurance rating. Consumer SSDs typically rate 150–600 TBW for 500GB–2TB drives.

In practice: a typical user writing 20–50GB/day to a 1TB SSD at 300 TBW would wear out the drive in: 300,000 GB ÷ 35 GB/day ÷ 365 = approximately 23 years

Consumer SSDs are outlasting their practical usefulness in most cases. High-write workloads (databases, video editing, development with heavy compilation) should consider drive-class SSDs with higher TBW ratings.

How to use the Data Storage Converter on sadiqbd.com

1. Convert between storage units — GB, TB, GiB, TiB for comparing specifications
2. Calculate TBW-based lifespan — convert your estimated daily write amount to TB/year and divide into the TBW rating
3. Compare drive capacities — understand whether the 931GB shown on a 1TB drive is as expected (binary vs decimal conversion)

Frequently Asked Questions

Will SSD prices continue to fall? The pace has slowed. Physical limits on how densely cells can be stacked and how reliably higher cell-level densities can be manufactured mean the 10× per-decade price decline of the past two decades won't continue indefinitely. Current 300+ layer 3D NAND is approaching manufacturing complexity limits.

Are NVMe SSDs always better than SATA SSDs? For average consumer workloads, real-world performance difference is minimal. If you're building a budget system and the price difference is significant, a SATA SSD performs comparably for most everyday tasks. If budget allows, NVMe is worth it for responsiveness-sensitive workloads.

Is the Data Storage Converter free? Yes — completely free, no sign-up required.

Try the Data Storage Converter free at sadiqbd.com — convert between bits, bytes, KB, MB, GB, TB and their binary equivalents.