You lost 2 disks in the same array?

A RAID5 array can only support the loss of one disk – if the two that went were in one array you will have data loss. Your post seems to imply they’re in two different arrays though – in which case I’ve not seen that behaviour. Possible faulty new disk? Fault in another disk in that array?

Yep – if you lost two hard disks in the same Raid 5 array – say bye bye data.

RAID 5 does definitely allow you to lose one disk only. RAID 6 would allow you to lose two at any one time.

Presumably the RAID utility can see the drive as you’ve formatted it? Are you required to make it a member of the array first?