I was given a WD Blue hard drive from an old desktop that apparently had not been powered on for more than seven years. It still works and has already handled copying about 351 GB of data, but its health status has always shown "Caution" in CrystalDiskInfo. I also performed a quick full-drive zero write with Linux using dd. Is it reasonably safe to use for storage, or should I assume it could fail soon?
3 Answers
A drive that reports “Caution” should not be trusted with anything important, even if it currently reads and writes normally. It may continue working for years, or it could fail without warning. Use it only for replaceable data and keep another copy of anything you care about. Check the full S.M.A.R.T. attributes and logs with a diagnostic tool such as Victoria or smartctl; the overall warning alone does not show which metric triggered it.
Writing zeros to the entire disk only proves that it survived that particular read/write workload; it does not repair the underlying issue or guarantee future reliability. Treat the drive as temporary or noncritical storage, and replace it if the S.M.A.R.T. results show increasing errors, pending sectors, or reallocated sectors.
The warning usually means one or more S.M.A.R.T. values have crossed a vendor-defined threshold, such as reallocated or pending sectors. The disk may still appear perfectly healthy during normal use, but that does not make it reliable. A live Linux environment and the smartctl utility can provide the raw values and error log for a closer diagnosis.

I checked it with CrystalDiskInfo already. Is there anything useful that Victoria or smartctl would show beyond the basic health screen?