SSD, HDD Reliability More Similar Than Thought
New data from Backblaze suggests that the reliability gap between hard drives and SSDs is not as large as previously thought and does not favor SSDs to the degree some had believed. The previous degree of difference between SSDs and HDDs was at least partly due to mismatched timelines.
Backblaze’s top-level data set leans decisively towards SSDs, but this is due to respective age of the SSDs versus the HDDs in the sample data set. Many products follow what is known as a bathtub curb: Devices either fail almost immediately, due to manufacturing defects, or they last for quite some time before failure rates begin to rise. As devices approach end-of-life, the failure rate increases. This forms both sides of the bathtub.
When Backblaze adjusts its data set for the relative age of both SSDs and HDDs, much of the variance between them falls away:
Backblaze writes: “Suddenly, the annualized failure rate (AFR) difference between SSDs and HDDs is not so massive. In fact, each drive type is within the other’s 95% confidence interval window. That window is fairly wide (plus or minus 0.5%) because of the relatively small number of drive days.”
The overall drive failure pattern for SSDs is moving similarly to HDDs as time passes, though the peaks are a bit lower and the same amount of time has not passed in total.
One thing to keep in mind: Backblaze’s dataset is based on its own backup business and does not necessarily address every user market, or even one of the most common markets. A customer evaluating an SSD versus an HDD isn’t solely concerned with a drive’s innate chance of failure over time. There’s also the question of how the drive will withstand shock. Laptops take a fair bit of punishment, and solid state storage is may be much better than spinning disks when it comes to withstanding impact.
SSDs are not always the best choice for every task, especially when bulk capacity is more important than raw performance, but they’re going to be the best option for most PC users, especially where primary drives are concerned. The performance advantage of SSDs are too large to ignore and Backblaze’s data doesn’t suggest SSDs are less reliable than hard drives — only that there may not be much daylight between the two.
SSD manufacturers have been facing other reliability concerns of late. Lower-end drives from multiple manufacturers are being shipped with weaker specs than what was initially shipped to the review community, with drives from Samsung, WD, and Crucial known to be impacted.
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