NAND

2 articles

Tech 16 Sep 2026 5 min read

SSD Garbage Collection Amplifies Host Writes

An SSD can write substantially more data to NAND than the host sends to the device. The extra traffic appears when the controller must relocate still-valid pages before reclaiming flash blocks that contain invalid data. This internal movement is write amplification. It is a consequence of the mismatch between fine-grained logical updates and NAND erase constraints, not an extra write issued by the application. NAND pages cannot be overwritten in place NAND flash is programmed in pages but erased in larger erase blocks. A page that already contains programmed data cannot generally receive an arbitrary in-place replacement. The controller writes the new version to another available page and marks the old physical page as stale in its mapping state.

Storage SSD

Tech 15 Sep 2026 6 min read

Flash Wear Leveling Spreads Erase Cycles Across NAND Cells

NAND flash has a finite endurance budget. Programming changes stored charge, but cells cannot simply overwrite arbitrary existing data in place. Pages are programmed inside larger erase blocks, and an erase operation resets a block before its pages can accept fresh programming. That geometry creates an endurance problem. A workload may update the same logical address thousands of times even though the drive contains many other blocks that receive almost no writes. If every logical address stayed permanently tied to one physical location, a small hot region could reach its erase-cycle limit while much of the flash remained lightly used.

Flash Storage NAND