What does SMART ID 187 (UECC Count) actually mean for real world data integrity?

[jerubedo]

Hello everyone,

So I have the Sandisk Extreme Pro 960GB SSD. It's had a grand total of 1.7 TB of data written to it over the course of about a year. Yesterday I decided to check on the SMART data and I noticed that the UECC count (ID 187) was 9 (raw data). So I ran a short and extended SMART test. Both passed. I ran a bad sector check as well. None to speak of. HOWEVER, I noticed that the UECC count incremented by 1 during the sector check. So I ran it again. And again, it incremented by 1. Each bad sector check puts the read data count up by 1TB, so for each TB read the UECC count increments by 1. This leads me to believe there is exactly 1 bad ECC module in the drive. My question:

What does this actually represent? Doing a few hours of Google research I understand what ECC is and what an Uncorrectable ECC means, BUT what does it REPRESENT? Will the disk fail? Will there be corrupted data? And if so will it only be on that one sector with bad ECC?

My wife also has the exact same drive and her UECC Count is 7 currently (again, a year of usage about). Hers also has 1 Reallocated sector. Hers is a boot drive and mine is just a storage drive. Here is an image of the SMART attributes from my drive from Sandisk Dashboard:

Note, all other attributes are A-OK. Thank you in advance for the help!!!

Here is the CrystalDiskInfo as well:

 

[Elixer]

Just means that for some reason, it couldn't correct it via hardware ECC.
If it is a one time thing, then, don't worry too much about it, but, as always, you need to keeps backups.
If that keeps increasing, then, there could be a electrical interference problem.
Right now, your SSD firmware most likely tried to do its magic on the cell to see if it needs to mark it bad or not.

 

[jerubedo]

Just means that for some reason, it couldn't correct it via hardware ECC.
If it is a one time thing, then, don't worry too much about it, but, as always, you need to keeps backups.
If that keeps increasing, then, there could be a electromechanical problem.
Right now, your SSD firmware most likely tried to do its magic on the cell to see if it needs to mark it bad or not.

Thank you for the response! As stated above, the count does indeed increase for every TB of data read. I doubt the problem is electromechanical since there are no moving parts in an SSD. I feel like it could be a firmware or Sandforce Controller problem. But it's also happening on my wife's drive. I've also RMA'ed my drive three times because of this "issue" and each one has had this happen either immediately, after a few months, or in this case after a year. It does have a 10 year warranty, but honestly I got this drive to have peace of mind for my valuable data, so if this represents potential data loss or corruption I'd rather just scrap this drive and get some other brand.

 

[Elixer]

Thank you for the response! As stated above, the count does indeed increase for every TB of data read. I doubt the problem is electromechanical since there are no moving parts in an SSD. I feel like it could be a firmware or Sandforce Controller problem. But it's also happening on my wife's drive. I've also RMA'ed my drive three times because of this "issue" and each one has had this happen either immediately, after a few months, or in this case after a year. It does have a 10 year warranty, but honestly I got this drive to have peace of mind for my valuable data, so if this represents potential data loss or corruption I'd rather just scrap this drive and get some other brand.

Um, heh, sorry, used the wrong term. I was stuck in HD mode, I meant that it could be electrical interference that causes this issue.
It also doesn't really matter which brand you get, there are none of them that will guarantee your valuable data, hence the reason you need to backup that data--especially since it is valuable.
Since you already did 3 returns, and it still does it, replace your cables, and move the SSD to another location if it is by the PSU.
It might also be a firmware issue as well.

Personally, I wouldn't worry about it, until you start to see other (major) SMART attributes start to increase as well.
If you want to do more testing, make a archive of anything (around 100GB or so), use 7zip or winrar.
Then, move said file a few times on the SSD.
Then do a archive test, and see if it passes.

 

[jerubedo]

Um, heh, sorry, used the wrong term. I was stuck in HD mode, I meant that it could be electrical interference that causes this issue.
It also doesn't really matter which brand you get, there are none of them that will guarantee your valuable data, hence the reason you need to backup that data--especially since it is valuable.
Since you already did 3 returns, and it still does it, replace your cables, and move the SSD to another location if it is by the PSU.
It might also be a firmware issue as well.

Personally, I wouldn't worry about it, until you start to see other (major) SMART attributes start to increase as well.
If you want to do more testing, make a archive of anything (around 100GB or so), use 7zip or winrar.
Then, move said file a few times on the SSD.
Then do a archive test, and see if it passes.

Thank you again! I've already tried changing cables, and it is as far from the PSU as possible. I ran an archive check as you suggested (copied over 100GB zipped folders 9 times) and the integrity check/checksum passed, so I guess I won't worry about it too much. The only reason I was concerned was becasue my main drive is the Samsung 850 Pro 1TB and it's had about 20 TB of data written to it over a year and a half and it has not logged a single error in that time (no RMA's or anything). Likewise with a Muskin drive I have in another computer (45 TB over 5 years). Maybe the Sandisk firmware is just more generous with logging errors? Who knows. Anyway thank you again for your input!