Elite Bug Hunter
If you're gauging speed from data copy to it from your troubled drives, the limiting factor is likely the troubled drives.
As for SMR drives, you will see normal performance until you hit the write threshold at which point you will know it as it will tank far below the speeds you're seeing now, like 10 MB/s area.
using a known good drive as a source turns out it went from 100MB/s down to 50MB/s then 20MB/s.
if i wait for ~5 minutes then initiate copy again. it went up to 100MB/s again then finally stabilize at 20MB/s again.
it never reaches as low as 10MB/s