Individual consumer MLC cells can only provide 3,000 to 10,000 write cycles, while enterprise MLC cells can handle 20,000 to 30,000 write cycles. In the enterprise, eMLC can serve as a compromise between inexpensive MLC flash and very expensive single-level cell (SLC) flash.
Typically, eMLC is 2-bit, while consumer MLC flash is 3 or 4-bit. In general, the more bits a flash cell has, the fewer write cycles it will have. Because eMLC flash media has more program-erase (P/E) cycles than consumer MLC, it has greater endurance and can tolerate the types of workloads that enterprise applications require.
A primary focus of eMLC vendors is to further improve write endurance and make MLC flash as reliable and long-lived as SLC flash. There are a number of techniques that vendors are using to improve write endurance, including:
- Distributing input/output (I/O) evenly across the entire flash drive, an approach called wear leveling.
- Improving the unrecoverable bit error rate (UBER) by creating better algorithms.
- Prolonging the time before the drive becomes unreliable by over-provisioning the flash media.
- Reducing write amplification.