"zpool status" will show if there have been errors reading data from individual devices. If a drive experiences enough failures, at least on illumos and Solaris-based systems, it will be marked degraded or faulted and removed from service. You can view individual failures on these systems with "fmdump -e". Here's a made-up worked example:
https://blogs.oracle.com/bobn/entry/zfs_and_fma_two_great