It thinks that its out of write cycles, however I pushed a 2TB samsung 980 pro to 7PB and it was fine, so ymmv. It did get slower after a while, but not unbearably so. I have been at 0% for 2+PB.
I only use it for irreplaceable data that I only have one copy of though.
Newer (think post 2015) nvme drives have secure erase.
The way it works is the drive is encrypted w/ a key transparent to the user. Issuing the secure erase clears the key in the firmware of the drive rendering all data useless. Then it goes into a state to zero the drive which cannot be interrupted (all commands to the drive go unanswered, if the drive has power it will zero until its done)
Hdds? Maybe self encrypted enterprise drives exist but I have personally never used one.
grep dmesg and see if the link is at sataII speeds, if so its almost certainly the cable. If not, still might be ok. Your motherboards IC may perfer some sata ports over others when its at its limit. Remember it likely runs on a 1x pcie bus back to the system bus which is ~ 800MB/s. You have 8 drives so...
Only panic when there isnt a lot of data being pushed and the drive still performs badly and you have replaced cable