Original source: https://www.cod3r.com/2024/08/backblocks/
Relevant part:
What about caches? The source for badblocks makes an effort to bypass the Linux disk cache but modern hard drives have a cache on the controller board. The typical options for a modern hard drive would result in the program writing 512kB, reading the freshly written data, moving to the next 512kB of the disk, and repeat until reaching the end of the drive. So, what will a modern hard drive do when it is told to write 512kB and immediately read that same 512kB when it has an on-board cache (256MB) of over 500 times that size? Wouldn’t it just read the data from the cache instead of the physical disk? Why has no one in all of the discussions of badblocks seemed to have noticed the read/write cycle involves far less data than can be stored in the disk’s on-board cache? Does this do anything real at all when it comes to testing the physical layer of the disk?
Is this true? and if so, is testing with badblocks on modern drives (even ones that are smaller than badblocks so called limit) essentially useless?
If not, why not?
Thanks!