Adding disk to volume on RN214

Thanks Stephen,

I'd not noticed that option!

I've included that log below, it doesn't look too positive...

Thanks

-- Logs begin at Thu 2020-04-16 11:21:37 GMT, end at Thu 2020-04-16 14:50:15 GMT. --
Apr 16 11:23:02 NAS-BTH rn-expand[2123]: Trying auto-extend (grow onto additional disks)
Apr 16 11:23:02 NAS-BTH rn-expand[2123]: auto_extend: Checking disk sda...
Apr 16 11:23:02 NAS-BTH rn-expand[2123]: auto_extend: Checking disk sdb...
Apr 16 11:23:02 NAS-BTH rn-expand[2123]: auto_extend: Checking disk sdc...
Apr 16 11:23:02 NAS-BTH rn-expand[2123]: sdc has enough free space for data-0 [7804599886]
Apr 16 11:23:02 NAS-BTH rn-expand[2123]: Preparing disk 0:2 (sdc,ST4000VN008,3726GB) for RAID data-0...
Apr 16 11:23:02 NAS-BTH rn-expand[2123]: prepare_disk: Prepare disk 0:2 (sdc,ST4000VN008,3726GB) with partition size 7804599855
Apr 16 11:23:02 NAS-BTH rn-expand[2123]: Found sdc is not a member of root
Apr 16 11:23:06 NAS-BTH rn-expand[2123]: Partitioning failed! [4]
Apr 16 11:23:06 NAS-BTH rn-expand[2123]: output: Warning! Read error 5; strange behavior now likely!;Warning! Read error 5; strange behavior now likely!;Creating new GPT entries in memory.;Warning! GPT main header not overwritten! Error is 5;Warning: The kernel is still using the old partition table.;The new table will be used at the next reboot or after you;run partprobe(8) or kpartx(8);GPT data structures destroyed! You may now partition the disk using fdisk or;other utilities.;Warning! MBR not overwritten! Error is 5!;Warning! Read error 5; strange be
Apr 16 11:23:06 NAS-BTH rn-expand[2123]: adding partition failed [5]
Apr 16 11:23:06 NAS-BTH rn-expand[2123]: Found sdc is not a member of swap
Apr 16 11:23:06 NAS-BTH rn-expand[2123]: Partitioning failed! [4]
Apr 16 11:23:06 NAS-BTH rn-expand[2123]: output: Warning! Read error 5; strange behavior now likely!;Warning! Read error 5; strange behavior now likely!;Creating new GPT entries in memory.;Unable to save backup partition table! Perhaps the 'e' option on the experts';menu will resolve this problem.;Warning! An error was reported when writing the partition table! This error;MIGHT be harmless, or the disk might be damaged! Checking it is advisable.;
Apr 16 11:23:07 NAS-BTH rn-expand[2123]: Partitioning failed! [4]
Apr 16 11:23:07 NAS-BTH rn-expand[2123]: output: Warning! Read error 5; strange behavior now likely!;Warning! Read error 5; strange behavior now likely!;Creating new GPT entries in memory.;Unable to save backup partition table! Perhaps the 'e' option on the experts';menu will resolve this problem.;Warning! An error was reported when writing the partition table! This error;MIGHT be harmless, or the disk might be damaged! Checking it is advisable.;
Apr 16 11:23:07 NAS-BTH rn-expand[2123]: add_partition: Input/output error [5]
Apr 16 11:23:07 NAS-BTH rn-expand[2123]: prepare_disk failed: Input/output error
Apr 16 11:23:07 NAS-BTH rn-expand[2123]: Trying xraid-expand (tiered expansion)
Apr 16 11:23:07 NAS-BTH rn-expand[2123]: Considering X-RAID auto-expansion for data
Apr 16 11:23:07 NAS-BTH rn-expand[2123]: Checking if RAID disk sda is expandable...
Apr 16 11:23:07 NAS-BTH rn-expand[2123]: Checking if RAID disk sdb is expandable...
Apr 16 11:23:07 NAS-BTH rn-expand[2123]: No enough disks for data-0 to expand [need 2, have 0]
Apr 16 11:23:07 NAS-BTH rn-expand[2123]: 0 disks expandable in data
-- Reboot --
Apr 16 14:31:36 NAS-BTH rn-expand[2160]: Trying auto-expand (in-place)
Apr 16 14:31:36 NAS-BTH rn-expand[2160]: Considering inplace auto-expansion for data
Apr 16 14:31:36 NAS-BTH rn-expand[2160]: Checking if RAID disk sda is expandable...
Apr 16 14:31:36 NAS-BTH rn-expand[2160]: Trying auto-extend (grow onto additional disks)
Apr 16 14:31:36 NAS-BTH rn-expand[2160]: auto_extend: Checking disk sda...
Apr 16 14:31:36 NAS-BTH rn-expand[2160]: auto_extend: Checking disk sdb...
Apr 16 14:31:36 NAS-BTH rn-expand[2160]: auto_extend: Checking disk sdc...
Apr 16 14:31:36 NAS-BTH rn-expand[2160]: sdc has enough free space for data-0 [7804599886]
Apr 16 14:31:36 NAS-BTH rn-expand[2160]: Preparing disk 0:2 (sdc,ST4000VN008,3726GB) for RAID data-0...
Apr 16 14:31:36 NAS-BTH rn-expand[2160]: prepare_disk: Prepare disk 0:2 (sdc,ST4000VN008,3726GB) with partition size 7804599855
Apr 16 14:31:36 NAS-BTH rn-expand[2160]: Found sdc is not a member of root
Apr 16 14:31:40 NAS-BTH rn-expand[2160]: Partitioning failed! [4]
Apr 16 14:31:40 NAS-BTH rn-expand[2160]: output: Warning! Read error 5; strange behavior now likely!;Warning! Read error 5; strange behavior now likely!;Creating new GPT entries in memory.;Warning! GPT main header not overwritten! Error is 5;Warning: The kernel is still using the old partition table.;The new table will be used at the next reboot or after you;run partprobe(8) or kpartx(8);GPT data structures destroyed! You may now partition the disk using fdisk or;other utilities.;Warning! MBR not overwritten! Error is 5!;Warning! Read error 5; strange be
Apr 16 14:31:40 NAS-BTH rn-expand[2160]: adding partition failed [5]
Apr 16 14:31:40 NAS-BTH rn-expand[2160]: Found sdc is not a member of swap
Apr 16 14:31:41 NAS-BTH rn-expand[2160]: Partitioning failed! [4]
Apr 16 14:31:41 NAS-BTH rn-expand[2160]: output: Warning! Read error 5; strange behavior now likely!;Warning! Read error 5; strange behavior now likely!;Creating new GPT entries in memory.;Unable to save backup partition table! Perhaps the 'e' option on the experts';menu will resolve this problem.;Warning! An error was reported when writing the partition table! This error;MIGHT be harmless, or the disk might be damaged! Checking it is advisable.;
Apr 16 14:31:42 NAS-BTH rn-expand[2160]: Partitioning failed! [4]
Apr 16 14:31:42 NAS-BTH rn-expand[2160]: output: Warning! Read error 5; strange behavior now likely!;Warning! Read error 5; strange behavior now likely!;Creating new GPT entries in memory.;Unable to save backup partition table! Perhaps the 'e' option on the experts';menu will resolve this problem.;Warning! An error was reported when writing the partition table! This error;MIGHT be harmless, or the disk might be damaged! Checking it is advisable.;
Apr 16 14:31:42 NAS-BTH rn-expand[2160]: add_partition: Input/output error [5]
Apr 16 14:31:42 NAS-BTH rn-expand[2160]: prepare_disk failed: Input/output error
Apr 16 14:31:42 NAS-BTH rn-expand[2160]: Trying xraid-expand (tiered expansion)
Apr 16 14:31:42 NAS-BTH rn-expand[2160]: Considering X-RAID auto-expansion for data
Apr 16 14:31:42 NAS-BTH rn-expand[2160]: Checking if RAID disk sda is expandable...
Apr 16 14:31:42 NAS-BTH rn-expand[2160]: Checking if RAID disk sdb is expandable...
Apr 16 14:31:42 NAS-BTH rn-expand[2160]: No enough disks for data-0 to expand [need 2, have 0]
Apr 16 14:31:42 NAS-BTH rn-expand[2160]: 0 disks expandable in data