R102 Netgear backup Fail: destination is read-only.

Marto73 wrote:
Bruce, 4 points. (a) Is Continuous protection on, for the Share being backed up? Could you try hourly/ daily? (b) Latest F/ware is V6.1.8 (c) Can you advise manufacturer and model # of USB. (d) You can't rule out a hardware issue with 2nd HDD. Regards, Marto

Thanks Stephenb - I found the myriad posts on read-only - and have been wading through them narrowing things down.
One useful outcome is to attempt to prevent spin down - which I will try next.. as indicated here amongst others http://www.readynas.com/forum/viewtopic.php?f=109&t=71608
The WD Knowledge base reports that Smartware may be able to change this setting:

WD external hard drive spins down after several minutes of inactivity Answer ID 1376 | Last Updated 02/25/2014 Most WD external hard drives will spin down (enter into power saver mode) after 10 minutes of drive inactivity. Once the drive is accessed again, the drive will exit from the power saver mode and spin back up. Note: This is a permanent feature of most of our external hard drives and cannot be disabled. WD externals that include WD SmartWare 1.6.X can use the software to change and/or disable this feature.

Marlo73:
a) I believe I turned this on recently, I'll try turning it off (but the backup succeeded on the other drive so not sure this would cause it on only one of the two..
b) Haven't yet been brave enough to update firmware on a production system - specially with backups not 100% !
c) 1TB USB3 WD Elements WDBUZG0010BBK-PESN
d) True Dat. Might try formatting it and backing up a different nas, and/or running the diags on the disk - but difficult/impossible? without cracking open the case?

In the past on this same machine I had the issue of the drives rapidly flling to capacity... so I agree the frontview backup functionality is still woeful (or is this just because its a "low" non-business model)?

I don't want to have to manually create rsync jobs to the usb as described here http://www.readynas.com/forum/viewtopic.php?f=31&t=74531 (and so be able to control things such as excluding snapshots)