I think a hard drive died. Should I see some sort of warning?

Thank you for the detailed response! I was at a loss for a starting point.

Output of ‘btrfs fi show’ confirms that a drive is ‘missing’. I’ve determined which one it is and replace it with a good drive, and instead of rebuilding I think I’ll see if I can mount the array as is and copy the things I most want to keep. Then I’ll start over with raid 10 as you suggest. Thanks!

[root@weiland mnt2]# btrfs fi show
Label: 'rockstor_rockstor'  uuid: 150c532d-d963-463e-9c2d-c806f46655aa
	Total devices 1 FS bytes used 8.13GiB
	devid    1 size 105.80GiB used 46.02GiB path /dev/sde3

warning, device 1 is missing
warning devid 1 not found already
checksum verify failed on 3137863680 found BA8DD541 wanted 5E6E68F7
checksum verify failed on 3137863680 found BA8DD541 wanted 5E6E68F7
bytenr mismatch, want=3137863680, have=0
Label: 'weiland'  uuid: 7aa74f0e-55a2-4f4e-8b65-83d39a5463f4
	Total devices 5 FS bytes used 3.23TiB
	devid    2 size 2.73TiB used 895.50GiB path /dev/sdb
	devid    3 size 2.73TiB used 895.50GiB path /dev/sdc
	devid    4 size 2.73TiB used 895.50GiB path /dev/sdd
	devid    5 size 2.73TiB used 895.50GiB path /dev/sdf
	*** Some devices missing