01-26-2021, 04:01 PM
If you replace two 4TB drives with two 8TB drives, you will only gain 4TB of extra storage space https://www.synology.com/en-uk/support/R...B|8%20TBIf you get an expansion unit, you will get extra 8TB. Yes, it is a seperate volume and RAID connected via eSATA. But you gain more space. And even if cable breaks, your RAID will not get damaged. DSM is smart enoguh to detect this. Surely it is not great to power on an extra unit and considering another NAS would make sense. But in this case I would rather geta 6 bay model or bigger. Slide all those drives in there and have couple of bays free for the future upgrade. I hope this helps.