So you investigate the iSCSI feature of the NAS box and discover a free, unsupported, iSCSI initiator for OSX and you think - brilliant! Mount a huge remote NAS drive and it appears to the OS as a locally attached external SCSI drive. Perfect. Time Machine would (presumably) work, so would anything else you'd expect to work on a local drive. And a quick test shows that it mounts quickly, transfers quickly, looks resilient.
So you repartition the RAID in the NAS for this purpose, which takes another 16 HOURS, then when you get round to making your first test bulk file transfer to the iSCSI volume, the Mac freezes a gigabyte in to the copy.
So that's good and stable then.
So it's goodbye iSCSI, and hello AFP.
Except... and this is so painful I can hardly stand it, when copying files via AFP, their creation and modification date is reset to whatever time and date the file was copied.
It's fecking APPLE FILE PROTOCOL, with an APPLE talking to it.
Web searches indicate that this is a very common gripe with regards to Macs. Even using 'cp' with the option to preserve as much metadata as possible (-P? -p?) fails, FFS. And so does 'ditto' and so (apparently) does rsync.
Desk - head - bang - repeat.
I think the answer is going to end up being to mount a sparseimage on the remote volume which has been mounted via SMB. This SHOULD (yet to be tested) surely preserve all metadata, but has the drawback that it will not be accessible from non-macs in the house, which is to say the Linux boxes, which is a pisser. Although possibly iSCSI is as dodgy on Linux as it would appear to be on this NAS box.