Error detection can always be used, but error correction may or may not be available (it depends on the type of block). Metadata blocks are redundant even on a single drive pool; so if you just have a partial failure (e.g. overwrite a metadata block) it might be able to correct the block using another redundant copy on the same drive. Data blocks will require a redundant pool configuration, though, as these are not store redundantly by default (e.g. multiple drives in a raidz or mirror).
Actually you can correct data blocks, on a single-drive ZFS pool, if you set the attribute copies=2 (ditto blocks): https://blogs.oracle.com/relling/entry/zfs_copies_and_data_p... Obviously this redundancy feature makes you use twice the disk space you would normally use.
