This is how long it takes to expand a NAS volume

It takes a looooooooooong time!

All.  Thought I would provide my experience from a recent upgrade of my NAS capacity. I was running out of space on my 5.44TB volume (around 500GB free):

OS 6.4.2 on legacy Ultra 6

Before upgrade:

4x1.5TB 5400rpm Samsung HD154UI

1x1.5TB 5900rpm Seagate ST1500DL003-9VT16L

1x2TB 5900rpm Seagate ST2000DL003-9VT166

RAID-6 dual redundancy.  Total volume was 5.44TB useable with 500GB wasted on the 2TB disk.

Sourced 3x3TB Seagate Backup external drives (5900rpm) and cracked them open

Used an existing 7200rpm desktop 3TB from my RN102 backup box (NAS RN102 4TB+3TB (6.3TB) JBOD)

After upgrade:

2x1.5TB 5400rpm Samsung HD154UI

1x3TB 7200RPM Seagate ST3000DM001-1E6166

3x3TB 5900RPM Seagate ST3000DM003-2AE167

RAID-6 dual redundancy. Total volume 8.06TB useable. Nothing wasted. New free space is now ~3.2TB

2TB seagate was swapped to the backup NAS to now be 4TB+2TB (5.45TB JBOD)

I swapped the disks one-at-a-time and the NAS rebuilt each time.

It took ~11 hours per disk - for 4 disks = 44 hours

The 4th disk swap needed me to destroy my back-up volume to use the 3TB disk (no backup!)

Once rebuilt for the 4th time, the expansion kicked-off straight away!! And took no time at all!

Then the new array needed to be re-sync'd - which has taken.....40 hours.

Total time = 84 hours = 3.5 days.

~5TB Back-up is now underway to the re-created backup JBOD from the freshly-sync'd 8TB volume.  Will take another day or so.

That's my experience!