Disk drive diagnostic tool are they definitive ?

Now you mention it , it’s not the quickest no , that was something I was planning to look into later, do you know how I can fix this and align the sectors ? I’m guessing it’s a factory reset using 4.1.7 or 4.1.8 ?

Yes, upgrading to 4.1.7 or later (you've already done this), verifying update is successful (i.e. new version shown in Frontview and/or RAIDar), a backup and a factory reset is the way to fix it.

Of course there are other performance tweaks you can make too. See ReadyNAS Performance Expectations

your a star thanks for your help mdgm , will do that :-)

alan27 - one never really knows when a drive may fail. You may not experience a failure in drives 2-4 for a long time. When I set up my NV+ over 4 1/2 years ago with two 500GB Seagates, one failed in a little over a month. The second one was still going strong when I upgraded the drive size last summer and it had over 25,600 hours on the drive. Hopefully you will not have another drive failure for some time, but one just never knows.

Thanks for the advice guys. I know where I stand now on this, I guess the best thing to do is make sure you have a good backup ;-)