ata4: command 0xca timeout, stat 0xd0 host_stat 0x1
ata4: translated ATA stat/err 0xd0/00 to SCSI SK/ASC/ASCQ 0xb/47/00
ata4: status=0xd0 { Busy }
sd 3:0:0:0: SCSI error: return code = 0x8000002
sdc: Current: sense key=0xb
ASC=0x47 ASCQ=0x0
Info fld=0x4acec6
end_request: I/O error, dev sdc, sector 4902614
Buffer I/O error on device sdc5, logical block 4902488
lost page write due to I/O error on sdc5

And as you can guess, ata4’s sdc is one of the new disks, not the old one that was failing already. Okay, next week’s schedule: replace the disk. Up to then, I can’t do much more.

And Seagate’s Seatools proved useless for the second time, as both drives passed the test with flying marks.