Time required to restore RAID array on LS421DE?

[Taurantres]

I have an LS421DE. One of the (4TB) drives failed last weekend. I replaced it with new drive and followed all of the steps laid out by Buffalo for replacing a failed drive. The array is accessible, but almost a week later NAS Navigator still indicates the array is rebuilding (rebuild started on 2/11; today is 2/18). The red light on the Linkstation is flashing red as though the disk(s) are being read. Is this timeframe for rebuilding an array reasonable for a 4TB mirrored array? Thanks.

[1000001101000]

It depends on several factors but more than a day or two would have me concerned. If my math is at all correct:

4tb=4,000,000mb
at a pessimistic 50mb/s is 80,000 seconds or 22 hours

Also note that the red leds aren't disk activity indicators, i beleive the manual describes what they mean in detail.