Tech blog  March 22, 2016


How long will my SSD last? Will it wear out within the same time-frame as a traditional hard-disk drive? These are important questions that many people will find themselves asking when it ’s time to buy a new drive. There are currently two metrics in-use that paint a somewhat murky picture.

When looking under the “endurance” heading of a technical specification sheet, a user will typically find either TBW (Terabytes Written) or DWPD (Drive Write Per Day). Though these metrics mean different things, at their foundation, they are both used to convey the same thing: what sort of endurance the user can expect from their storage drive. Both of these terms are used to supply the user with a quantitative rating to better understand how long their drive might last. Though many SSD vendors typically choose to show just one of these metrics, as both fundamentally convey the same information.

TBW is a measure of how much data can be written to the drive before it is likely to fail. DWPD on the other hand takes into account the capacity and warranty offered by the manufacturer. It measures how many times the entirety of the drive can be erased and completely re-written in a day for the lifetime of the warranty. So for example, if an SSD has a DWPD rating of “1”, a capacity of 1TB, and a warrant y of 3 years, the manufacturer is rating their drives to withstand complete re-writes of 1TB once a day, every day, for three years, before the drive is likely to fail. The TBW rating is a bit more straightforward: if a drive has a rating of “100”, it can withstand 100 TB of data to be written onto the drive (total) before it becomes likely to fail.

In enterprise environments, the reliability of an array can easily become the most important and expensive component. And now that we are armed with this new knowledge, it is easy to recognize the differences between “consumer-level” and “enterprise-level” SSDs. The consumer-grade drives typically see TBW ratings that are much lower when compared to their enterprise-grade counterparts, meaning their ove rall lifetimes will be much shorter. If the TBW rating of a particular SSD is 2, or 3, or even 5 times higher than another one, the cost-savings can be seen through lower replacement rates throughout the lifetime of the array.

An SSD with a high TBW rating means higher reliability; high reliability means measurable savings in costs, time, and headaches. Understanding these ratings can be the difference between having SSDs that need to be replaced every year, versus those that can withstand a much longer turn-around. When thinking long-term, SSDs with enterprise-grade reliability should always be prioritized.

Article by: Israel Imru

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