SSD roundup techreport

Solid state drives, when they first appeared on the market, weren’t all that good. They offered minimally higher lifespans than hard drives and much more impressive data protection against physical damage, but the memory cells didn’t last very long and no-one was sure at which point they’d break. Over the last six years they’ve since become orders of magnitudes tougher and durable, so much so that now they’re outstripping hard drives in speed and longevity.

A few months ago, Tech Report’s Geoff Gasior started testing SSD longevity with a specific mind to how long SSDs would last when they’re being written to constantly. I’ve been following Geoff’s findings and the most recent one in particular is very surprising as he passed the 600TB write mark.

Yes, that’s 600TB, or over 300GB of new data being written to the SSDs every day for five years straight. It’s way higher than the 22TB that most brands guarantee and it’s also much higher than most people will ever be able to achieve in the drive’s lifespan. Geoff’s point that SSDs are far more durable than hard drives at this point was already well noted at the 100TB mark – 600TB is just insane.

reallocated sector count

As Geoff points out in his most recent assessment, the TLC NAND memory on Samsung’s 840 continues to see errors the cells and automatically reallocates data to healthy sectors over time. Right in the beginning of the tests all the drives passed the 22 and 100TB mark without issue but the regular 840 sees more cells from its provisioned sectors being reallocated to replace failing ones. The curve is generally linear so this indicates that the cells are dying out in a regular fashion associated with normal wear and tear.

However, most users would have replaced their drives long before the 100TB mark and the reallocated sectors are well within the 23GB limit that Samsung uses for drive provisioning. Most other SSDs see no issues until the 840 Pro starts to see failing cells at the 600TB mark. TLC NAND is much less hardy than MLC NAND and degrades at a faster rate. Still, it’s a lot cheaper than other solutions.

avg writes over time

Write speeds over time see a small decline at 600TB for most drives but strangely the Corsair Neutron GTX sees increased write speeds over time. The Neutron series is powered by the LAMD LM87800 controller and 19nm Toshiba NAND memory. That’s also the same recipe in the Seagate 600 line, so things should be similar there as well.

In the write speed tests, it’s possible that the Neutron GTX is optimising write speeds over time to preserve performance, whereas it appears that other drives like Intel’s 335 series or Samsung’s 840 family do see a general dip in overall write speeds over time.

Overall, Geoff’s testing and results go a long way to dispove the myth that SSDs are less durable than their mechanical counterparts – they aren’t. If anything, a mechanical drive would have likely died long before reaching the same level.

Source: Tech Report

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