Sector remapping has been used for hard drives for a long time. A read failure has to occur first, and then the next write to the bad sector will go to a new sector in the reserve area. Therefore, it does not prevent data corruption.
I actually had bad sectors on a SSD which I just replaced. When the anti-virus software started scanning the files, my computer would hang for a long time with the data LED solidly lit. That was how I found out about the issue.
I thought some of the better drives relocated data automatically on both, read and write errors (assuming a second read was successful). Anyway, thatās why mirroring is needed.
Since weāre discussing backups and related topics, Iāll mention that I have been very happy with this service for a year or so now. (I had been using one of the consumer backup solutions that went awayā¦ I forget which one now!)