I have a ReadyNAS3220 that is low on space. It currently has 12 4TB drives in a RAID6 configuration. Can I add larger drives to this WITHOUT data loss or rebuilding the array? I have found information that I can for other models of Netgear NAS, but nothing specific to this model.
If you're using X-RAID (or re-enable that if not using it currently) you can replace the disks one at a time, wait for the resync to complete then move onto the next disk. You'll need to replace at least four disks to get vertical expansion as you're using RAID-6.
You should backup your data just in case.
Also it would be advisable once the volume has expanded a bit to update to newer firmware. 6.2.4 is very old firmware.
During the resync/expansion of the volume, the performance may be impacted. You may get lower throughput and higher latency. The resync will take hours to complete, and more if the volume is under load. This is something to keep in mind for your datastore(s).
As well as taking a backup, maybe you want to Storage vMotion your most critical and/or latency sensitive VMs to another storage prior to the operation.
