Article: KB-031

This page provides shows you how to test your system’s SSD endurance or life span and learn about the endurance formula, SMART attributes to use, and software to test endurance.

A simple way to visualize SSD endurance is to think of a box in the figure below. The surface is the capacity of the raw NAND on the SSD. Data is written on the entire surface, then erased and re-written – up to the program erase cycle (PE) of the SSD. In the figure below, we use 3,000 PE cycles as an example.

The formula for Terabyte Written (TBW) is the surface multiplies the PE and divide Write Amplification (WA). WA is the effect of wear leveling and garbage-collection by the SSD.

The figure below illustrates how to calculate Write Amplification (WA). We take the delta of the host writes divide the delta of the NAND writes. To keep things simple, we assume the entire surface is written. This way, we can use erase count to derive NAND writes.

The figure below lists the key SMART attributes of the StorFly and how to use them in formulas in your software to calculate life remaining, TBW, and life used.

How long to test? How many writes are enough?

With workloads or usage, the system needs to run to have enough read/write cycles for an accurate estimation.  The timeframe varies by workload and could take several days.

Write Amplification is only valid for one workload. See illustration on the right. Therefore, we want to test and recalculate endurance when host software is changed.

In the lab environment, to estimate the SSD’s endurance, we fill the drive a few times to write enough data to activate all firmware mechanisms (wear level, garbage collection, read disturb management, etc.).

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Software Tools

We recommend the following software tools.

  • vtView to collect SMART data. It is a tool provided by Virtium.
  • vdbench by Oracle. This tool is best to generate workload tests (JEDEC219).

How to Test

We recommend the following procedure when you test SSD endurance or life span. We need SMART data to calculate life span and endurance.

  1. Collect SMART data periodically. vtViewCmd helps you automate this task. vtViewCmd collects data and formats them in CSV format.
  2. Run your applications as usual or run traffic generation software (like vdbench) to simulate workloads.
  3. Load the vtView log file to this link to analyze SSD life span. vtView lets you know if it can analyze or needs more time to collect enough writes.

vtView works for all of our SSD products such as SATA SSD, NVMe SSD, CF, CFast, and eUSB.