By Joel Hruska on May 11
SSDs have a number of advantages over conventional hard drives. They draw less power, they’re an order of magnitude faster, and while they remain more expensive in absolute terms, the size of that gap has shrunk markedly over the past few years. There is one downside to SSDs, however — long-term data retention remains a significant issue.
A recent presentation by Alvin Cox of JEDEC demonstrates just how large the gulf is between enterprise and client drives. Temperatures while active and in storage are both listed. If a drive is stored at 25C or operated 40C, expected data retention for a client drive is 105 weeks, or nearly two years. Let the storage temperature creep up to 30C, or 86F, and the drive should still hold data for an entire year.
NAND-Data-Retention
Enterprise SSDs, however, have entirely different characteristics. An enterprise drive stored at 25C and operated at 40C has a retention rate of just 20 weeks. In worst-case scenarios or high storage temps, the data on an enterprise drive can start to fail within seven days. 3D NAND, which uses an older manufacturing process, might rate better in such metrics, but JEDEC doesn’t include that information.
These timelines aren’t likely to make much difference to consumers, who keep devices in daily use, but they do matter in the long-term and outside client usage scenarios. If you’re a serious computer enthusiast, you likely have a collection of drives that you removed from old systems when you built a new machine. Some people will carefully step through and ensure that each and every bit of data from the old installation was archived to local backup or cloud storage, but it’s much more common for people to copy the critical data and leave the rest of their information on the original disk. With a mechanical drive, that’s not a problem — you can take a drive out of rotation and typically assume it will spin back up two years later, provided you store it properly.
With SSDs, you can’t necessarily depend on more than 12-24 months of longevity — and if you bought into the SSD craze from 2008 – 2011, chances are you’ve now got at least one drive you’ll be retiring in the not-too-distant future. High-end consumers who might be tempted by enterprise-level NAND drives need to pay attention to the brief unpowered data retention times — in this case, buying an enterprise drive really might not be the best choice for a system that remains unpowered for any length of time.
Note that the temperature range for proper storage of SSDs is far smaller than for hard drives. A hard drive can typically be stored from -40 – 70C (-40 – 158F. Yes, -40C = -40F). In order to maintain proper data longevity, SSDs, in contrast, may need to be stored in climate-controlled environments. Granted, most people likely don’t stick a drive in a normal storage unit, but this data suggests that even a few days in a car in summer could meaningfully damage long-term data retention.
Enterprise awareness
Businesses and corporations need to be particularly aware of this limitation of enterprise flash. As a blog post at Kore Logic points out, there are serious legal ramifications for a company that fails to preserve business records that were stored on NAND flash. The IRS typically recommends that individuals and small businesses save tax data for at least seven years; large publicly traded companies have additional regulations to follow to satisfy laws like Dodd-Frank and Sarbanes-Oxley.
Beyond SEC regulatory requirements, there’s always the chance that a major company could find itself needing to refer back to years-old documents in order to settle a legal case. Again, proper data preservation is vital to such efforts — and for now, spinning disks (or in some cases, tape backup) offer a longevity that SSDs simply can’t match.
SSDs are amazing — and properly deployed, absolutely worth the investment — but the data retention challenges are real. We recommend everyone engage in proper backup procedures and be aware of the limitations of your chosen medium. No single storage type is perfect — so don’t depend on just one way of backing up critical information.
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