HGST He10 - read errors that fixed spontaneously

[Springdale]

Hi,

This is not directly related to data recovery, it's rather a very interesting story and I'd like to know your opinion.

I have bought a HGST He10, model number HUH721010ALE600 from eBay as failed/parts only. Description: when reading from the drive, pending sectors are created.
Initial testing shown that the seller was right - the drive initialized and basically worked correctly, however starting a sequential read test revealed the problems:

Stopping the test and letting the drive idle resulted in repeated audible read retries as the drive kicked off its offline scan. Now the interesting part. When writing to the drive, the sectors were not reallocated but removed from the pending list. I rewritten the drive sequentially 2-3 times and the read problems went away and haven't came back - the drive has a perfectly clean SMART and is working in a NAS for storing temporary data more than a year ago! The past problems are still recorded in the SMART Error Log:

I'd like to know your opinion, what could be the problem?
- Media or head contamination that cleared itself and particles are trapped in the filter
- Poorly written data maybe due to excessive vibration ("soft bad sectors")
- The drive is refurbished. Maybe there was an error in the recertification process?

Any comment is appreciated. Let's discuss!

[fzabkar]

It appears that one head in the outermost zone has a few weak sectors. If a sector is marked for reallocation, the drive retests it and returns it to service if it passes.

[Springdale]

Thanks for the reply. Seems correct, but what happened? I can no longer reproduce any error, not even a single raw read error in SMART. I have stress tested the drive with iometer for days, no issue.

[fzabkar]

Test the drive with Victoria or HDDScan and see if it records any "slow" sectors, ie sectors which require read retries.

[Springdale]

Test the drive with Victoria or HDDScan and see if it records any "slow" sectors, ie sectors which require read retries.

Thanks for the suggestion - I use HD Sentinel and no slow sectors at all. Not a single read error, SMART raw value of Raw Read Error Rate stays at 0 all the time. The disk just seems perfect. Have a look at the SMART. The only thing that is a bit odd is that the Helium containment status attribute's normalized value is 97 while the raw value is 100, but I don't think it has any significance.

And I would like to stress that I'm not going to sell the drive as flawless or something like that. I just would like to know more about how a hard drive works

[Springdale]

Any ideas on what happened? I guess no one can tell if the drive will develop problems again in the future?