I'm running version 4.7.
I recently had to take 3 disks out of my array because they failed at the same time. I figured I could live with losing 1/7 (5TB) of my data, and could eventually replace most of it via recovery tools, reripping etc.
So I was rebuilding parity with my remaining 17 disks, the largest of are 2 TB. Just at 73.5%, one of the 1.5TB drives began to accumulate errors and writes to parity have stopped it seems. It's currently at 74.5% and the 'main' display of unraid seems to think that parity build is continuing as normal. Here's an excerpt from the syslog, which is mostly repeats of what I've included:
Dec 8 20:58:22 MediaServer kernel: handle_stripe read error: 2909546072/3, count: 1
Dec 8 20:58:22 MediaServer kernel: md: disk5 read error
Dec 8 20:58:22 MediaServer kernel: handle_stripe read error: 2909546080/3, count: 1
Dec 8 20:58:22 MediaServer kernel: md: disk5 read error
Dec 8 20:58:22 MediaServer kernel: handle_stripe read error: 2909546088/3, count: 1
Dec 8 20:58:22 MediaServer kernel: md: disk5 read error
Dec 8 20:58:22 MediaServer kernel: handle_stripe read error: 2909546096/3, count: 1
Dec 8 20:58:22 MediaServer kernel: md: disk5 read error
Dec 8 20:58:22 MediaServer kernel: handle_stripe read error: 2909546104/3, count: 1
Dec 8 20:58:22 MediaServer kernel: md: disk5 read error
Dec 8 20:58:22 MediaServer kernel: handle_stripe read error: 2909546112/3, count: 1
Dec 8 20:58:22 MediaServer kernel: md: disk5 read error
Dec 8 20:58:22 MediaServer kernel: handle_stripe read error: 2909546120/3, count: 1
Dec 8 20:58:22 MediaServer kernel: md: disk5 read error
Dec 8 20:58:22 MediaServer kernel: handle_stripe read error: 2909546128/3, count: 1
Dec 8 20:58:22 MediaServer kernel: md: disk5 read error
Dec 8 20:58:22 MediaServer kernel: handle_stripe read error: 2909546136/3, count: 1
Dec 8 20:58:22 MediaServer kernel: md: disk5 read error
Dec 8 20:58:22 MediaServer kernel: handle_stripe read error: 2909546144/3, count: 1
Dec 8 20:58:22 MediaServer kernel: md: disk5 read error
Dec 8 20:58:22 MediaServer kernel: handle_stripe read error: 2909546152/3, count: 1
Dec 8 20:58:22 MediaServer kernel: ata1: translated ATA stat/err 0x41/04 to SCSI SK/ASC/ASCQ 0xb/00/00
Dec 8 20:58:22 MediaServer kernel: ata1.00: device reported invalid CHS sector 0
Dec 8 20:58:22 MediaServer kernel: ata1: status=0x41 { DriveReady Error }
Dec 8 20:58:22 MediaServer kernel: ata1: error=0x04 { DriveStatusError }
The affected disk, md5, is also showing 0C as its temperature. I've never had a problem with disk 5.
OT: What I have had lots of problems with is WD Green drives. All the bad drives I've had in the past two years, except for firmware issues with Samsung F4 and a Seagate, have been WD drives. I must have had about 8 bad ones.