Raid 1 issue

I have a weird case where i cant mirror the second volume on my hard drives. The mirror had to be restored since the disk 1 some how fell off the Raid 1. Well i got the second first volume to mirror but the second wont and when i check the capacity was not the same. They were 1MB off and the first volume was not. Could that be the issue why volume 2 wont mirror. I have 2 1TB split, volume 1 = 30GB and Volume 2 = 968.