Aqui é um artigo recente sobre a experiência do Google com SSDs. Foi baseado em:
- Millions of drive days over 6 years
- 10 different drive models
- 3 different flash types: MLC, eMLC and SLC
- Enterprise and consumer drives
Key conclusions
- Ignore Uncorrectable Bit Error Rate (UBER) specs. A meaningless number.
- Good news: Raw Bit Error Rate (RBER) increases slower than expected from wearout and is not correlated with UBER or other failures.
- High-end SLC drives are no more reliable that MLC drives.
- Bad news: SSDs fail at a lower rate than disks, but UBER rate is higher.
- SSD age, not usage, affects reliability.
- Bad blocks in new SSDs are common, and drives with a large number of bad blocks are much more likely to lose hundreds of other blocks, most likely due to die or chip failure.
- 30-80 percent of SSDs develop at least one bad block and 2-7 percent develop at least one bad chip in the first four years of deployment.
- SSD UBER rates are higher than disk rates, which means that backing up SSDs is even more important than it is with disks. The SSD is less likely to fail during its normal life, but more likely to lose data.