What to do when Surface Scan finds bad blocks


Whether you have a Solid State or Rotational Drive, Techtool Pro's Surface Scan test may discover bad blocks at some point. A bad block, or bad sector, is a portion of the disk that can no longer be written to. Both types of devices utilize a cache of spare blocks that are used when bad blocks are found in order to ensure that your data does not get corrupted by storing it on a bad block. When the Surface Scan test finds bad blocks, this means that this cache is no longer able to use spare blocks, and your data will be at risk of corruption.

Surface Scan Catalina

In almost all cases, discovering bad blocks means that the drive will need to be replaced. Bad blocks represent physical problems with a disk, and cannot be repaired in software. In rare cases, a rotational drive can get a small lease on life by performing a secure erase on the disk. For rotational drives, this can cause the cache to reset, and may provide a few additional spare blocks. This generally does not work on solid state drives, however.

So it's worth taking the time to run the Surface Scan test to find bad blocks before they start causing problems, or to identify a likely reason your Mac isn't working as it should. Even though it takes time, it can ultimately save many hours of fruitless searching for the cause of unexplained or erratic behavior from your computer. Even though bad blocks mean that a drive needs to be replaced, the cost to replace the drive is trivial compared to losing important data.

Pro Tip: Start up using a Protogo device or an eDrive on an external disk in order to perform a Surface Scan on your internal startup disk.