The solution depends on the message you receive.
error on Plex plex_name while reading volume volume_name offset ## length #
If the volume is mirrored, no further action is necessary because the alternate mirror’s contents are written to the failing mirror. This is often enough to correct media failures.
If this error occurs often, but never leads to a plex detach, there may be a marginally defective region on the disk at the position indicated. Eventually, you may need to remove data from this disk (see the vxevac(1M) manual page) and reformat the drive.
If the volume is not mirrored, this message indicates that some data could not
be read. The file system or other application reading the data may report an
additional error, but in either case, data has been lost. If you like, you can partially salvage the volume and move it to another location.
error on Plex plex_name while writing volume volume_name offset ## length #
The disk reporting the error is failing to correctly store written data. If the volume is not mirrored, consider removing the data and reformatting the disk.
If the volume is mirrored, it will become detached and you should replace or reformat the disk.
If this error occurs often, but never leads to a plex detach, there may be a
marginally defective region on the disk at the position shown. Eventually, you may need to remove data from this disk (see the vxevac(1M) manual page) and reformat the drive.