Unlike mechanical hard drives, whose operation is based on turntables and moving heads, SSDs have no moving parts and information is stored directly on their NAND chips. These chips have a life time limited by the number of write and erase cycles, so there comes a time when they reach their limit and the unit is rendered useless. However, we have never heard of anything similar on hard drives … is it your infinite durability?
The lifetime of a hard drive is not infinite
As we have mentioned, the operation of a hard disk is based on its plates, which rotate at a fairly high speed that is usually, generally, 7,200 or 5,900 revolutions per minute. At the same time, they have one or more moving heads that move across the surface of the platters to read and write the information, which is why a mechanical hard drive makes noise and generates vibrations in many cases.
The simple fact of having moving parts already means that it is impossible for a hard disk to have an infinite lifetime, since no matter how well the device is designed, certain friction occurs both when rotating the platters and when moving the reading head. and writing, and friction inevitably produce a wear that entails, sooner or later, the failure and the unit death.
The difference with SSDs is that their wear is internally in their NAND chips memory, while wear on a hard drive occurs on bearings and friction areas. However, if you wonder if the number of writes and erase cycles on the platters of a hard disk it is infinite, the answer is that theoretically yes it is; in this case there is no wear and tear and the sectors of the disc plates are capable of changing their state (from peaks to valleys, ones and zeros and vice versa) as many times as you want, there is no set limit.
In this regard, while SSD manufacturers indicate their TBW to indicate their useful life or durability, hard drive manufacturers indicate the MTBF (Mean Time Between Failures) that reflects the mean time between failures; the MTBF on a hard drive refers to the number of hours it is turned on and is nothing more than a statistical average that generally does not reflect reality at all, since on a hard drive this value is usually 1.2 million hours and from then no one has a hard drive for so long and all of us have ever failed one.
For this reason it is much more reliable to look at another value called AFR (Annualized Failure Rate), which is expressed as a percentage and reflects the probability that the disk will fail during a year of 24 × 7 use. This percentage is usually quite low (less than 1%) and continues to indicate a probability and not a specific data as in SSDs, but even so it serves better to get an idea of the useful life that we can expect from each hard drive.
In short, the useful life of a hard disk is roughly equal to modern SSDs, which can already last several dozen years depending on use. It may be more, it may be less, but of course a hard drive has a lifetime and is not infinite.