Post your entire log, read the stuff at the top of the topic.
I/o errors are generated by your drive and it simply means that your firmware/media/drive are not playing well together. You may be using Verbs, but they can be made in India (crap), your firmware needs to be updated, your drive is on its' way to the bone yard....but we don't know because you didn't follow the easy stuff above. And we hate guessing games.