A quick and dirty way to do it is to use Microsoft's Robocopy. I've used this in the past and you can set the flags on for the copy to not only copy the files but also preserve the permissions of the files. The shares would be specific to the NAS appliance you are using so most likely you'll have to recreate those.
I would also think depending on the NAS, there would be some sort of replication ability to do a bit by bit copy and then just the differentials after the initial data move. Storage companies like NetApp have this capability. Or there should be 3rd party replication software available. You'll have to check on these options.
For me, I have my NAS/fileserver running as a VM. I can either do a snap shot of it via VMware or do it at the block level on my iSCSI arrays doing a snap shot there too. With this option there wouldn't be a traditional upgrade per say with replacing the entire NAS setup. The upgrade would happen at the physical host level for the VM or at the block storage level.
I would also think depending on the NAS, there would be some sort of replication ability to do a bit by bit copy and then just the differentials after the initial data move. Storage companies like NetApp have this capability. Or there should be 3rd party replication software available. You'll have to check on these options.
For me, I have my NAS/fileserver running as a VM. I can either do a snap shot of it via VMware or do it at the block level on my iSCSI arrays doing a snap shot there too. With this option there wouldn't be a traditional upgrade per say with replacing the entire NAS setup. The upgrade would happen at the physical host level for the VM or at the block storage level.