Your SSD Is Bigger Than It Says

A consumer 1 TB SSD contains more than 1 TB of NAND flash — often 1.07 TB, sometimes 1.1. The extra chips are there; the operating system just never sees them. This reserved capacity is called overprovisioning, and without it a modern SSD would be unusable.

Flash memory has a physical problem: each cell can only be rewritten a limited number of times before it goes bad. Consumer TLC flash typically tolerates a few thousand program-erase cycles per cell. If the drive always wrote to the same cells, a busy user could burn through them in months.

Overprovisioning gives the controller room to spread writes around. When you rewrite a file, the controller doesn't erase the old cells immediately — it writes the new data to a fresh pool of hidden cells and marks the old ones as reclaimable. A background process, garbage collection, eventually erases them in bulk. The end result is that every cell gets roughly equal use, and the drive outlasts the warranty.

Enterprise SSDs push overprovisioning further, sometimes reserving 28% of capacity. That's why a 960 GB data-center drive and a 1000 GB consumer drive can use the same physical chips — the enterprise one is running the same flash with more slack.