ReadyNAS NV+ v1 wont sync one of its 4 drives

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gmunyard wrote:

Cannot raise the total volume above 5533GB although it should be around 7400 (4 X 1859GB).

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Let's start here.  A 4x2TB RAID-5 array has a raw size 8 TB (~7.27 TiB or ~7400 GiB).  But that includes 2 TB of RAID parity blocks that protect the data.  The volume capacity is actually 6 TB (~5.45 TiB).  So the volume size you are reporting is in fact correct.  If you are seeing a volume capacity around 4 TB (~3.63 TiB), then there is a problem.  Please let us know if that's the case.

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gmunyard wrote:

Took it out of its original slot #2 yesterday and erased it in a dock connected to my MacBook Pro, then reinserted it as a fresh drive in slot #4 after shifting original drives in slots #3 and #4 down. Went through sync process again, but still not adding additional volume to total storage. 

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This is expected behavior in a healthy RAID volume.  With all disks in place, the array status is "redundant" - meaning that the data is protected from a single disk failure (or removal of a disk). 

Then when you remove a disk, the volume becomes degraded, but the capacity doesn't change. The degraded volume is no longer protected and if a disk were to fail (or another disk is removed), the volume will fail and all data on it is lost. 

When you reinsert the disk, it resyncs and the volume becomes redundant again (with no capacity change).  The resync process reconstructs the disk content from the remaining three disks, so it will end up with the same content as you had before you removed it.

Are you seeing the "redundant" status in Frontview (or in RAIDar)?

BTW, I generally don't recommend shuffling the disks around.  While the NAS will work if you do that, in your system one of the disks is quite different from the rest.  Newer ReadyNAS distribute the parity blocks in a regular pattern across all the drives.  However, your ReadyNAS has a dedicated parity disk instead, and that disk is formatted differently. When things go wrong it is sometimes useful to know which disk is the parity disk. Normally that is disk 4, but if you shuffle you won't know which one it is.  You probably shouldn't try to re-order them at this point.  But if you do a factory reset in the future, I suggest preserving the slot order.  Personally I put a label on each disk tray, identifying it's slot.