Transcend's industrial SSD lineup uses two NAND types with different endurance characteristics. The MTS570T uses SLC (single-level cell) NAND, which stores one bit per cell and is rated for approximately 60,000 P/E cycles. The SSD460T and MSA370I use 3D TLC (triple-level cell) NAND, rated for 1,000 to 3,000 P/E cycles depending on the NAND generation.
SLC NAND lasts longer per cell, but Transcend's industrial SLC drives ship in lower capacities (64GB to 256GB typical). A 128GB SLC drive in an ATM writing 5GB of transaction logs per day reaches its endurance limit in roughly 4 to 5 years of continuous operation. The controller firmware tracks wear using SMART attributes (Media Wearout Indicator, Available Reserved Space). When spare blocks run out, the firmware has nowhere to relocate data from worn-out cells. The drive either enters read-only mode or the firmware crashes.
TLC industrial drives have lower per-cell endurance but higher capacity. The SSD460T in a POS terminal with a 512GB drive writing 10GB/day may last 3 to 4 years before the TLC cells degrade beyond the error correction threshold. Transcend implements a form of pseudo-SLC mode (sometimes marketed as SuperMLC) on some industrial TLC drives, writing one bit per cell to extend endurance at the cost of reduced usable capacity.
In all wear-out scenarios, the data stored on the NAND does not disappear when the cells degrade. The bits become less reliable to read, requiring more aggressive error correction. PC-3000 SSD reads the NAND at a low level with configurable read retry parameters, applying multiple voltage thresholds to extract data from degraded cells that the drive's own firmware could no longer read.
