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SSDs and SMART Data

There can be some confusion about what SMART data actually is. The acronym SMART stands for Self-Monitoring, Analysis and Reporting Technology. A SMART enabled storage drive monitors itself and collects data, and this data can be read and interpreted with the help of utilities capable of reporting the SMART data to the user. While this seems pretty straight-forward, there are a few things you need to be aware of as you interpret your SSD’s SMART data.

A lot of utilities for reporting SMART data were designed for hard drives, and because they are, they tend to not report SSD data correctly. The SMART attributes of an SSD are not organized in the same way the attributes of a hard drive are, primarily because most of them don’t apply to a drive that is lacking any kind of moving parts.

This means that although the SMART data reported by an SSD will be correct and valid for the SSD, the attributes may not be correctly identified, which for can lead to confusion. For example, when the “Power-on Hours Count” attribute reports a number to the utility, an incompatible utility may incorrectly label that number “Program Fail Count” or “Reported Uncorrectable Errors”. When that happens, a perfectly good SSD is incorrectly reported as a failing drive to the customer attempting to read the SMART data, all because he or she is not aware that they are using a utility that isn’t compatible with their SSD. It is very important to use a utility that can correctly read the SMART layout of your SSD.

In regards to the attribute named “Percentage Lifetime Used” (sometimes referred to as “Percent Lifetime Remaining”), this is simply a metric for how much wear life is left on your SSD. A solid state drive, like any flash memory-based storage device, has a limited amount of data which can be written to the memory blocks before they start to lose their reliability, and eventually go into read only mode. Your Crucial SSD will keep track of this life with SMART attribute 173, “Average Block Erase Count.” The Lifetime Used is a reflection of the block erase count in terms of a percentage. For example if your drive is rated for 3000 block erases and you have a total of 100, your Percentage Lifetime Used would be 100/3000, or 3-4%. For percent lifetime remaining we would simply take (3000-100)/3000 = 96-97%. These attributes are not a full picture of the health of a drive, but an expectation of how much usable life is left.

The Crucial® Storage Executive tool will correctly report the SMART data on all supported Crucial® SSD models. On storage drive models that are not supported by the Crucial Storage Executive, the tool will still report the SMART data. However, the attribute definitions will only be displayed for SSD models supported by the tool.

Another thing to remember is that SMART data is not a comprehensive diagnostic tool. Standard troubleshooting practices and operating system diagnostics are more reliable when it comes to determining the health status and reliability of an SSD than any SMART data read-out.

Incorrectly reported or interpreted SMART data can lead to incorrect conclusions which, unfortunately, can lead to an RMA of a perfectly functional drive.  Interpreted correctly, the SMART data from your SSD can be a useful tool in troubleshooting your SSD.

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