Sign in with
Sign up | Sign in

SSD Endurance Characteristics

SSD Endurance: Data Integrity is Marathon, Not a Sprint
By

If you visualize an enterprise data workload as a 50-foot yacht, you might ask whether you want to haul that yacht with a full-size V8 pickup truck or a compact hybrid. Drag that yacht with a hybrid and you’re going to be shopping for a new vehicle pretty soon. The same is true of lower endurance drives. A data center may well replace multiple low-endurance drives before wearing out a single high-endurance drive in the same environment and application.

If this sounds a bit too vague for comfort, know that the JEDEC Solid State Technology Association, previously known as the Joint Electron Devices Engineering Council (JEDEC), has matters in hand. JEDEC has long controlled industry specifications for DRAM (such as DDR system memory) and has recently started working in the SSD space to bring some coherency and standardization to endurance qualifications.

With two key publications, JESD218A, and JESD219, JEDEC lays down the industry’s first standard on testing SSD endurance and defining endurance workloads, respectively. Ultimately, JEDEC SSD endurance testing culminates in a “TBW” rating based on user-measurable interface activity. The TBW can be used to compare drives directly.

During testing, JEDEC requires that four conditions be met:

·         The SSD maintains its capacity

·         The SSD maintains the required uncorrectable bit error rate (UBER) for its application class

·         The SSD meets the required functional failure requirement (FFR) for its application class

·         The SSD retains data with power off for the required time for its application class

Because these TBW ratings apply to different application classes, we should briefly examine these classes. In the context of drive endurance, there are only two classes, client and enterprise, and they include the following characteristics:

Here is another look at these criteria focusing on temperature:


As you can see, the expectations placed on the two drive classes are quite different. Retention use refers to the duration over which data must be kept intact with no external power to the drive. The FFR and UBER numbers denote the number of allowable failures and errors in drives pushed to their endurance rating limits and then subjected to their retention time.