Linus Torvalds found out the hard way that solid-state drives (SSDs) aren't invincible -- and when they do fail, they can die without warning and at inconvenient times.
The creator of the Linux kernel blogged this week that the SSD in his workstation simply stopped working, interrupting his work on the Linux 3.12 kernel.
"The timing absolutely sucks, but it looks like the SSD in my main workstation just died on me," Torvalds wrote. "I had pushed out most of my pulls today, so realistically I didn't lose a lot of work."
While SSDs are vastly better performers than hard disk drives and are considered more reliable for mobile devices because they have no mechanical parts to break, they do have a limited lifespan. With some early SSDs, that lifespan ended up being less than a year, depending on the quality and use of the drive.
As an investigation into SSD reliability performed by Tom's Hardware noted: "We know that SSDs still fail.... All it takes is 10 minutes of flipping through customer reviews on Newegg's listings."
While there are no moving parts in an SSD, the semiconductor components can fail. For example, a NAND die, the SSD controller, capacitors, or other passive components can -- and do -- slowly wear out or fail entirely.
While Torvalds didn't specify the SSD manufacturer in his blog, he did write in a 2008 blog that he'd purchased an 80GB Intel SSD, likely the X25, which has become something of an industry standard for SSD reliability. The early X25's were built on top of the highest quality NAND flash chips available at the time.
Anecdotally, various editors at Computerworld have experienced failures related to OCZ-brand SSDs. But considering Torvalds' SSD may have been five years old, it would be hard to criticize its endurance - especially when it was being used in a workstation.
"I think the best way to describe SSD reliability is that thanks to controller maturation, average product endurance is improving and the standard deviation is falling," said Ryan Chien, an SSD and storage analyst with IHS's Electronics & Media division.
Although most client drives outlast their three-to-five year warranties, if Torvalds was subjecting such a drive to heavier workstation-type workloads, which happens a fair bit in enterprises, "the lifespan likely will not meet expectations," Chien said.
Multiple factors affect SSD reliability, according to Jeff Janukowicz, research director for SSD and Enabling Technologies at IDC.
The NAND flash media plays a key role, as its quality differs between manufacturers. And earlier generations of NAND flash have lower endurance characteristics related to bit errors -- when electrons leak through cell walls -- and program disturbs. A program disturb is the unintentional programming of a memory cell. Do it enough, and endurance suffers.