Ready NAS NV+ 4250 v3 drive migration

So your backup is not up to date? It's important to backup important data regularly and not just store it on the one device, no matter what device that is. Like all PCs a NAS will eventually fail.

Were you using X-RAID? Or if you were using Flex-RAID which RAID level(s) were you using?

The process for moving disks across from a Sparc ReadyNAS to an OS6 ReadyNAS is described in ReadyNAS: Migrating disks from RAIDiator 4.1 or RAIDiator 5.3 to ReadyNAS OS 6

This would result in purchasing a data recovery contract for support to attempt to recover your data. We don't know what state your disks, array, volume etc. are in without looking at it.

Another option is to use an ordinary x86 machine running Linux. There is a straightforward process to attempt if you were using X-RAID or certain Flex-RAID levels. However if things aren't in a good state then this may not work.

Btw there is no RN412. If you're using 3 or more disks (which you'd have to be to be using Flex-RAID RAID-5) then you'll need at least a 4-bay unit such as the RN424.