Failing RAID 5 rebuild / upgrade

[tealio]

I've been attempting to upgrade / rebuild a RAID 5 array since Wendnesday. For those reading later on, it's Sunday now.

I'm trying to migrate my data from a 3x1TB to a 3x2TB. I don't have enough SATA ports to have both arrays up, even if they're both running degraded with 2 drives each.

It has nearly rebuilt acouple of times, but it keeps failing near the end (around 99%).

I was able to catch the error message with dmesg | tail

[24817.339543] ata4.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x0
[24817.344244] ata4.00: irq_stat 0x40000001
[24817.348939] ata4.00: failed command: READ DMA EXT
[24817.353637] ata4.00: cmd 25/00:00:f0:0b:d5/00:04:6c:00:00/e0 tag 0 dma 524288 in
[24817.353638]          res 51/40:2f:b1:0f:d5/00:00:6c:00:00/e0 Emask 0x9 (media error)
[24817.372326] ata4.00: status: { DRDY ERR }
[24817.377020] ata4.00: error: { UNC }
[24817.389240] ata4.00: configured for UDMA/133
[24817.393942] ata4: EH complete

If it fails again this time (I'm at 95.5%) I'm going to try to run the array degraded and copy over the data to a new 2TB RAID1 1x2TB.

If that works i'll then add another drive to the RAID1.

I've read that converting a 2-disk RAID1 to a 3-disk RAID5 is possible. When i get to that point i'll need some guidance.

Until then, any translation of the error messages would be appreciated.