I discovered 2 of my old smaller drives are pretty bad off according to snapraid's SMART report. I built my first server with snapraid and mergerfs to pool a bunch of old drives. Then I added a new pair of 8tb drives after scouring Best Buy, one for storage and one for the new parity. Now I want to remove the 2 risky drives (device names sdd and sdb) permanently by copying their data to the sdc disk (still an old smaller disk but in good shape).
Since I pooled the disks and made a snapraid array, I have no idea how to copy data from individual disks before removing them. Any suggestions?