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Old 09-02-2010, 02:44 AM
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Yellowbeard Yellowbeard is offline
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Default Interpreting SMART Data on Corsair SSDs

In the last few weeks, I have spent quite a bit of time looking at the SMART data from a variety of Corsair SSDs. This thread is here to address the specific things I have observed about a few popular SMART reporting utilities, the SMART attributes and data, and the Corsair Force series SSDs.

I discovered some very interesting things about SMART monitoring and reporting. SMART as defined by the ATA standard is standardized. However, the structures or methods used by device manufacturers to report SMART attributes and status are not. Although there are some common standards observed across device manufacturers, there are many that are unique to each.

This problem is exacerbated by the fact that many SMART values have what is known as a raw value which is wholly determined by the device manufacturer. This raw value may or may not correctly correspond to a physical unit or normalized value, numbered 1-253. A great example of this is the recent issue of some SMART monitoring utilities reporting SSD temperatures of 156c or more!

Additionally, there are a set of SMART attributes that only apply to SSDs. And, even within these SSD specific attributes, there are variations of the terminology used for these attributes. Finally, to completely complicate things, not all SSD controllers report the same SMART attributes.

Many SMART tools were originally only designed to monitor HDDs. Some current tools are adaptations of older SMART utilities that have been modified or updated to include SSD attributes. Unfortunately, due to the variations of SMART attribute reporting across the many different SSD controllers, it is almost impossible to find a tool that is accurate across all brands of controllers AND that also correctly deals with all the SSD specific SMART attributes.

We are working dilligently with SandForce and with the developers of some of the more popular SMART monitoring utilities to improve the accuracy when using these utilities with Corsair SandForce based SSDs. In the mean time, here are some screenshots of some of these issues that you may want to be aware of. In short, if your drive is performing within specification, then you should be skeptical of any SMART utility that is indicating issues.

Keep in mind that this is not a condemnation of each respective software developer or criticism of their efforts. However, we feel it is important to show our customers some examples of what is going on as we work our way through this situation.

An important item of note is the method of determining Health Status or SSD Life Left. Some SSD controllers report an attribute not seen on SandForce attributes, 205 (hex-D0). This attribute is the MAX Program/Erase cycles for the SSD. This attribute is used on some controllers combined with atttribute 5 (Reallocated Sector Count aka Retired Block Count) to determine SSD Life Left. Since this attribute is not reported by the SandForce controller, it is impossible to determine how the monitoring utilities are determining SSD Life Left or Health Status reports.


Crystaldisk 3.7.0

In this example, we can see 2 different temperature attributes reported. Obviously a working drive is not at 0C and there is no raw or normalized value given.

This report is also problematic as the second attribute, E7 (aka 231) is still reported by some tools as a drive temperature. Here it is showing SSD Life Left which is an SSD attribute. However, we have also verified that the SandForce controllers are not currently reporting the E7 attribute correctly. So, we believe that it is not a reliable reporting of SSD Life Left.

As you can see, this drive is new having been cycled only 12 times and been powered on for 3 total hours. I took it out of the box, installed Windows 7, and took these screenshots. It has never been benchmarked. With so little usage, and these reporting anomolies, we don't believe that 96% is an accurate estimate of Health Status for this drive.





DiskCheckup

This utility, with a release date of August 19, 2010, shows several Unknown Attributes, some of which are circled in red. These attributes are reported by other tools including CrystalDisk. Therefore, it is unclear why this tool would not show known SMART attributes shown by other utilities.

We again see the E7/231 attribute reported incorrectly as a Temperature.





HD Tune

The Health Warning indication for attribute 05 is an erroneous reading. We are looking into this and have not as of yet determined why this occurs. This same drive checked with the SandForce utility does not show any status indicating an issue.

Again, we also see the SSD Life Left attribute E7/231 reported as a temperature. As previously stated, this attribute has been determined to not be reported correctly by the SandForce controller.




So what does all of this mean to end users? As stated above, we don't believe that the current SMART tools are completely accurate in their reporting. Our suggestion is to use performance as read by ATTO as a tool to determine if your drive is functioning properly. Remember, no SSD is going to report 100% life left, even fresh out of the box.
Attached Images
File Type: jpg F40 CrystalDisk 2.jpg (217.8 KB, 38700 views)
File Type: jpg F40 DiskCheckup 2.jpg (182.0 KB, 38468 views)
File Type: jpg F40 HD Tune 2.jpg (180.9 KB, 40721 views)

Last edited by Yellowbeard; 09-07-2010 at 02:13 PM.
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