Also note this in the disk logs, same on each disk ...
Aug 23 13:07:37 Tower kernel: ata1: SATA max UDMA/133 abar m2048@0x93300000 port 0x93300100 irq 30
Aug 23 13:07:37 Tower kernel: ata1: SATA link up 6.0 Gbps (SStatus 133 SControl 300)
Aug 23 13:07:37 Tower kernel: ata1.00: ATA-10: WDC WD40EFPX-68C6CN0, 81.00A81, max UDMA/133
Aug 23 13:07:37 Tower kernel: ata1.00: 7814037168 sectors, multi 16: LBA48 NCQ (depth 32), AA
Aug 23 13:07:37 Tower kernel: ata1.00: Features: NCQ-prio
Aug 23 13:07:37 Tower kernel: ata1.00: configured for UDMA/133
Aug 23 13:07:37 Tower kernel: sd 2:0:0:0: [sdc] 7814037168 512-byte logical blocks: (4.00 TB/3.64 TiB)
Aug 23 13:07:37 Tower kernel: sd 2:0:0:0: [sdc] 4096-byte physical blocks
Aug 23 13:07:37 Tower kernel: sd 2:0:0:0: [sdc] Write Protect is off
Aug 23 13:07:37 Tower kernel: sd 2:0:0:0: [sdc] Mode Sense: 00 3a 00 00
Aug 23 13:07:37 Tower kernel: sd 2:0:0:0: [sdc] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
Aug 23 13:07:37 Tower kernel: sd 2:0:0:0: [sdc] Preferred minimum I/O size 4096 bytes
Aug 23 13:07:37 Tower kernel: sd 2:0:0:0: [sdc] Attached SCSI disk
Aug 23 13:08:18 Tower emhttpd: WDC_WD40EFPX-68C6CN0_WD-WX62D62EYNAP (sdc) 512 7814037168
Aug 23 13:08:18 Tower emhttpd: read SMART /dev/sdc
Aug 23 13:08:38 Tower emhttpd: WDC_WD40EFPX-68C6CN0_WD-WX62D62EYNAP (sdc) 512 7814037168
Aug 23 13:08:38 Tower emhttpd: error: ckmbr, 2337: No such file or directory (2): open: /dev/sdc1
Aug 23 13:08:38 Tower kernel: mdcmd (2): import 1 sdc 64 3907018532 0 WDC_WD40EFPX-68C6CN0_WD-WX62D62EYNAP
Aug 23 13:08:38 Tower kernel: md: import disk1: (sdc) WDC_WD40EFPX-68C6CN0_WD-WX62D62EYNAP size: 3907018532
Aug 23 13:08:38 Tower emhttpd: read SMART /dev/sdc
Aug 23 13:08:48 Tower emhttpd: WDC_WD40EFPX-68C6CN0_WD-WX62D62EYNAP (sdc) 512 7814037168
Aug 23 13:08:48 Tower emhttpd: error: ckmbr, 2337: No such file or directory (2): open: /dev/sdc1
Aug 23 13:08:48 Tower kernel: mdcmd (2): import 1 sdc 64 3907018532 0 WDC_WD40EFPX-68C6CN0_WD-WX62D62EYNAP
Aug 23 13:08:48 Tower kernel: md: import disk1: (sdc) WDC_WD40EFPX-68C6CN0_WD-WX62D62EYNAP size: 3907018532
Aug 23 13:08:48 Tower emhttpd: read SMART /dev/sdc
Aug 23 13:08:54 Tower emhttpd: WDC_WD40EFPX-68C6CN0_WD-WX62D62EYNAP (sdc) 512 7814037168
Aug 23 13:08:54 Tower emhttpd: error: ckmbr, 2337: No such file or directory (2): open: /dev/sdc1
Aug 23 13:08:54 Tower kernel: mdcmd (2): import 1 sdc 64 3907018532 0 WDC_WD40EFPX-68C6CN0_WD-WX62D62EYNAP
Aug 23 13:08:54 Tower kernel: md: import disk1: (sdc) WDC_WD40EFPX-68C6CN0_WD-WX62D62EYNAP size: 3907018532