builtin ssd has bad sectors

Question

Level 1

8 points

builtin ssd has bad sectors

This is my new MacBook Pro 2017, with 1T built in SSD. It works just well, except some files became unusable occasionally. Now, the file system is formatted as APFS. But before upgrade to macOS 10.13 it's HFS+. Same thing happened on both of these FS. Though I can recovery the broken file from backup, there is a big change to loose my data. So, I have to backup my system frequently, and I need to solve it urgently.

This is how I tell the file is broken.

Method (1): When I copy the broken file to external hard disk by copy-and-paste or something like that. Error message popups as "The Finder can’t complete the operation because some data in xxx can’t be read or written. (Error code -36)".

Method (2): Test the file with "cp" command as the following:

cp xxx yyy

The output would be like:

cp: xxx: Device error

Left the file yyy created but of a smaller length, means "cp" command stopped at that point.

I'm sure there is no permission or file system issues in this situation.

So, did this means that the SSD is broken and I need to replace it?

MacBook Pro (13-inch, 2017, 4 TBT3), macOS High Sierra (10.13.2)

Posted on Dec 16, 2017 5:26 AM

Reply

Answer 1

Dec 16, 2017 7:31 AM in response to Nelson75 C

"Bad spots" are a problem seen since the very first rotating magnetic media (that were the size of a clothes washing machine). Throwing out an entire magnetic drum or disk when one tiny spot goes bad is an expensive nightmare. So all drives (including the built-in SSD) have always been built with a certain number of spare blocks, and a built-in mechanism for the drive controller to substitute spares on a permanent basis.

The drive controller cannot "fix" the data that are reading as Bad. But when new data are written, the controller can substitute a spare block for one that has been observed as Bad.

--------

If you have a way to restore the file (which is sitting in a bad block) from another source, your immediate problem will be solved, because the new copy will be written to different blocks. No drive replacement is necessary or appropriate unless/until the number of Bad Blocks is overwhelming or no more spares are available.

"in the old days" of SCSI drives, the drive would be completely re-written with a known pattern such as all Zeroes, and read back. Any block found to still be bad immediately after a good re-write would be spared out.

Today's SATA and later drive controllers make note of the block number(s) going bad, so much less re-writing is needed to substitute spares. I am not certain what procedure Apple suggests to repair a permanent SSD drive.

Reply

Answer 2

Nelson75 C Author

Level 1

8 points

Dec 16, 2017 11:30 PM in response to Grant Bennet-Alder

Thank you for detailed reply.

Yes, I totally agree with you. The problem is how common bad spots generates. It's a 1TB SSD, which I didn't use before. But my previous MacBook Pro with 256GB SSD, which I have used for 2 years, never have this situation. And this one, within 6 months, already have more than 20 broken files found, though it's very strange that the macOS system never crashed because of broken files. So, it's obviously that this 1TB SSD is not as strong as the previous 256GB one. I don't know if this is normal for a 1TB SSD, seems not likely. I think I need to have the main board changed (it's said the SSD is soldered on the main board, and cannot be changed seperately), as it's still in warranty.

Reply

Answer 3

Dec 17, 2017 6:47 AM in response to Nelson75 C

I know 20 bad blocks sounds like a lot, but as long as spares are available, it really is not many (considering just how many blocks there are).

Using Internet recovery or a USB-stick Installer to erase the ENTIRE drive and re-Install should give you all good blocks again. The ones on the Drive Controller's "Bad" list should have spares substituted.

That or a motherboard replacement both require you have a Trusted Backup. Extreme caution suggests having two, in case something also goes wrong with the first backup.

Reply

Answer 4

CT

Level 7

23,987 points

Dec 16, 2017 5:49 AM in response to Nelson75 C

Presumably this mac is still under warranty; I would take it in.

Reply