I have a ReadyNAS Pro Business Edition with six Seagate ST32000542AS 2T drives, set up in RAID Level 5. About a month ago, I discovered that disk 1 was reported as failed, and the ReadyNAS genereate the message "Detected increasing command timeouts  on disk 1 ... This often indicates an impdneing failure. ...". I rebooted and the ReadyNAS resynched, and no longer reported disk 1 as a problem. Then ten days ago, I got the same message for disk 6. I again rebooted, the ReadyNAS resynched and no longer reported disk 6 as a problem.
And now, I have the same problem reported on disk 2. It is currently resynching.
It seems strange to me to get reported failures on different disks. Each disk was placed in service in September 2010, and the ReadyNAS is used in my nome. The disks still have almost a year of warranty left.
I am wondering if this is just a case of the disks reaching the end of their lives, or is the ReadyNAS experiencing problems itself?