@mikrucio
well I work in a Computer repair store.. and I can tell you from 7 years of experience. Hard disk drives can and WILL slow down from 30mb/s to about 1mb/s for example.
They don't actually slow down per se. The slowdown is from read/write retries, or from the extra seeks resulting from
bad sector/track remapping.
To check if the HDD has any such blocks, check
S.M.A.R.T attribute 5 (Reallocated Sectors Count). Also attributes 196, 197 and 198 should be checked for.
Regardless, the actual physical disk access is exactly as fast as before. The areas that are not affected by the bit rot work at full original speed, for example.
That being said, it needs to be really severe case before it begins to affect the performance. Couple of dozen of remapping sectors will not affect performance, really.
NOT ALL hard disks will do this. some models are more prone than others.
Some HDDs are much more prone to failure, yes.
