Recommended Surface Scan App for Hardisks and SSDs for MacOS Big Sur?

Surface scan is meaningless with SSDs as there is no surface. The only low level useful tool for an SSD is a SMART status reader with the only meaningful items are Available Spare, Available Spare Threshold, Percentage used. Other than that, unlike HDDs, the internal SSD firmware is constantly changing things in order to optimize performance.

On the Mac that would Disk Utility's First Aid feature. It comes with every Mac and is located in the Applications/Utilities folder.

Only if you boot into another volume like the Recovery volume: (boot with the Command + R keys held down).

Otherwise it just verifies the drive and does no repair.

What do you mean by the term "surface scan"?

Surface scan mean, it scans the hardisk physically for bad sectors and marks that as unuseable, so it's never written with data.

The hard drive controller takes care of that on its own. You don't need to do it. The OS doesn't write to sectors. The OS tells the drive controller to write data to the drive. The drive controller writes the data. If it discovers a bad sector in the process, it maps it out to one of the reserves.

Alvin777 wrote:

...How about a similart app for SSDs that check that each cell of the SSD is not bad (preferably freeware or trial too), that's recommended?

Thank you.

SSD firmware automatically marks bad sectors and removes them from access and then replaces them with the drive's spare blocks and verifying any writes from pretty extensive cache. So bad blocks are impossible to write. So they cannot be written to. Unlike HDD, the sector map is dynamically changing because of the firmware's mapping is constantly updating because of of the internal functions as garbage collection which can move things all around then a new sector map is created. Also, such an app would create excessive wear to the SSD as in their process they need to generate write, which SSD blocks only have a limited number of.

Also, even modern HDDs have vastly improved their functionality in this regard.

Surface scans are a thing of the 80's when at the time mass storage technology simply was not as sophisticated as today and are really of not much use any more as drive firmware has become sophisticated enough in its error checking that it is simply not needed.

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As I understand it, when we use Apple's Disk Utility app, it does any needed repairs when possible and also marks bad sectors so they will not be used.