Measuring SSD/Flash Endurance
NAND flash SSDs have a limited number of write cycles before the cell fails, expressed as its endurance rating. The cause is physical: every time the drive writes/erases, the flash memory cell’s oxide layer deteriorates. The type of cell impacts the number of write cycles before failure. Notice that when you compare
SLC vs. MLC vs. TLC, you'll see key differences:
- SLC: Single-level cell NAND flash supports 50,000 to 100,000 write cycles.
- MLC: The 2-bit data multi-level cell (MLC) flash generally takes up to 3,000 write cycles. eMLC (enterprise MLC) sustains up to10,000 write cycles, and can reach 35,000 cycles on 3D NAND.
- TLC: Triple-level cells (3-bit) NAND flash is low at 300-1000 write cycles, and can achieve 1500-3000 write cycles with 3D NAND.
When you’re thinking about write cycles, also keep write amplification in mind. Writes are not simply single writes in the user or application layers. They are multiple writes for redundancy and crash consistency, where the controller copies data to provide redundancy. Additional sources of write amplification include de-duplication, filesystem writes, metadata and log structures, and garbage collection.
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