Readynas Pro 6 X-RAID 2 Dual Redundancy Proactive Drive Swap

Hi all,

I have a Pro 6 running 4.2.27 with 4x1TB Hitachi drives (approved on HCL) and am planning to proactively replace 2 of them so from a mechanical / wear perspective the drives in the volume are different. I've heard many horror stories of multiple drive failures when a failure does occur. I figure by having half of my volume on newer disks I reduce this risk to some extent.

Now... I would of course backup my unit (500GB data approx) and then replace one disk at a time, waiting for it to re-sync and become fully redundant. I would then leave a few days for it to settle in and then do another drive.

Is there anything I should be aware of or additional precautions I should take. If it is better I shut down the units rather than hot swap them, then I can do this also. I'm concerned as there are some horror stories on here with folks re-sync's taking days and days and then freezing rendering the whole volume useless.

Is there are rough amount of time each disk should take to re-sync and become redundant on a system with no users.

Thanks...