A new report from Google researchers has uncovered some interesting and unexpected facts on the lifespans of sold-state drives.
According to the report, it's the age of the SSD — as opposed to heavy usage — that determines when it's most likely to fail.
The report, titled ‘Flash Reliability in Production: The Expected and the Unexpected' from Google researchers Raghav Lagisetty and Arif Merchant (working with University of Toronto's Bianca Schroeder), analyzed 10 different models of drives from Google's data centers.
While multi-level cell (MLC) flash memory is considered less reliable than single-level cell (SLC) memory, the study also determined that there is little difference between the two in soundness, stating “SLC drives do not perform better for those measures of reliability that matter most in practice.”
This despite the study's finding that SLC drives did have significantly lower raw bit error rates.
Also uncovered in the study:
- SSDs have a much lower replacement rate than traditional hard disk drives (HDD). HDDs saw an annual replacement rate of 2-9%, while SSDs posted a 4-10% replacement rate over a four-year span — less than a third the annual rate of HDDs.
- Conversely, SSDs experience a far higher rate of uncorrectable errors. More than 20% of SSDs developed uncorrectable errors within four years, and 30-80% developed bad sectors. HDDs had much lower rates, with 3.5% showing bad sectors over a 32-month period.
So what does this all mean? SLC drives might not be worth the extra cost when compared to MLC drives; consumers and businesses with high data volumes can rest easier as wearing out flash memory isn't as much of a concern with today's SSD designs; and users should remain vigilant with their backup practices given the comparatively high error rates of SSDs.