We are living in a time where the quality of hard drives has been drastically decreased. The Vendors are struggling to improve the the capacity what is leading to ECC-Errors. Also the vulnerability for bad blocks has increased. Its no wonder that in one of my PCs an old IDE Spinpoint F1 by Samsung is doing its work while i already had to replace 3 drives within 2 years in my NAS. Because of the dead sectors.
Such dead sectors are blocks on the surface of an hard drive which are not writable due to physical damages. Facing bad blocks can be the sentence of death for a RAID Array.
But how can we be sure that an hard drive is healthy?
If everything looks just fine, as above, we would not have to be concerned, if there would not be the risk of bad blocks because they have the characteristic that they become conspicuous only if there are read or write actions performed to them. For ensuring that the array act correct we are going to perform a manual check:
Now we have to check that the “check” we have just sent to /sys/block/md42/md/sync_action produces an effect: