Hello!

If I format the drive, the UNC will still be marked?
I know that UNC means "Uncorrectable Data: An ECC error in the data field could not be corrected (a media error or read instability)" from bsnyder's post.
I read dencee's explanation dencee's explanation
But I still don't know:
If MHDD marked UNC, is it physical error unrecoverable or is it possible to repair it by format?
Is the information UNC indicates that the drive is physically damaged for sure?

UNC, in lay terms, means that the data written to a sector is no longer valid based on checksum tests.
UNC error does not indicate there is physical damage on the media, BUT it also does not mean there isn't any.

It's complex and can't really say safely one way or another without running more advanced tests on all drive components as a whole.
The only way to establish something concretely is to basically conclude something by analyzing results from all these tests as a whole. Obviously, deep understanding of theses tests is necessary, so that the interpretation of the tests' results is accurate.

Also, "repairing an UNC error" is a well known misnomer. An UNC can't be fixed. "To fix it", as in eliminate an UNC error from showing up, it is necessary to reallocate its space to another spare healthy sector.

I suggest reading MHDD manual and testing with it.

_________________
Hard Disk Drive (HDD), Solid State Drive (SSD, SATA, NVMe, etc), USB Flash Drive and RAID Data Recovery Specialist in Massachusetts

A format will cause the drive to retest the sector and return it to service if good, or reallocate its LBA to a spare if confirmed bad.

_________________
A backup a day keeps DR away.

Not always is possible to reallocate sectors.
A sector would be reallocated to spare only if gets accessible in somehow (example by many reading/writing retrys or by changing readiness timeouts), if a UNC sector is not accessible in any way then it will not be reallocated (this is called pending sector).

_________________
My firmware database:
https://mega.nz/folder/O01DkBRI

Thank you very much.
I formatted the HDD and I scanned by MHDD once again.
Instead of 9 UNC I have now 1 UNC and one warning.
What do you think about it?
We can say the HDD is damaged in this sector?

at OP
Read this again:

_________________
Hard Disk Drive (HDD), Solid State Drive (SSD, SATA, NVMe, etc), USB Flash Drive and RAID Data Recovery Specialist in Massachusetts

Use a tool (eg a disc editor or dd in Linux) to write something to that particular sector. That should force the drive to have make another attempt to reallocate it.

In fact you could use MHDD's FF command to write to a particular LBA:
http://real-world-systems.com/docs/MHDD ... al.html#ff

_________________
A backup a day keeps DR away.