For write errors on log and data subvolumes, XLV assumes that these write errors are hard errors (the disk driver and controllers handle soft errors). If the volume element with a hard error is plexed, XLV marks the volume element offline and ignores the volume element from then on. If the volume element is not plexed, the volume element remains associated with the volume and an error is returned.
XLV doesn't handle write errors on real-time subvolumes. Incorrect data is returned without error messages on subsequent reads.