DS920+ Expansion Guidance needed

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DS920+ Expansion Guidance needed

Operating system
  1. Windows
I have a DS920+ with 4 16TB drives manually configured as RAID 10 (may have been a mistake). I have reached 87% utilization, so I need to expand. I have been through the Synology support section with little luck. I did not use SHR.

1) Is it possible to replace (a drive at a time) two of the 16TB drives with 20 or 22 to increase the overall storage and have the unit transfer the data from the other drives? Thinking that I replace a drive, migrate old data to new drive, then replace its mirror and do the same? Or did I hose myself by not doing SHR at initial setup?

2) if #1 isn’t possible, is there a current Synology expansion unit that could be added?

3) If #1 and #2 are not viable, would it be possible to buy a new 6 or 8 bay enclosure and migrate the drives, and then add 2 additional drives to expand the RAID 10 array?

As pretty obvious, I am a noob with external NAS units.

The Help for replacing drives explains how to do this, including for RAID 10.

Reading the Help on adding drives it excludes RAID 10 from being supported: so that would stop expanding the storage pool through adding drives using an expansion unit (DX517) or moving them to a larger bay NAS.

So your #1 is possible but you won't realise any extra storage until all drives have been replaced. This does seem like an expensive way to add a few extra TB, unless you are going to secure wipe the 16 TB drives and sell them.

#2 is possible with the DX517, but only if you create a second storage pool and volume on it. This is the recommended way, i.e. don't span a storage pool across the main and expansion units. But note that there'll be a DSM partition on all drives so the single, interconnecting eSATA cable will be maintaining the data storage and OS operation.

#3 is also possible but you still have to create a second storage pool and volume.

You may well have been better choosing SHR with 2 drive resilience (a.k.a. SHR-2), which is more like RAID 6. If you see RAID 10 then there's the risk that two drives fail and all data is lost due to striping across the two RAID 1. I guess it all depends on why you chose RAID 10, which applications needed the better latency with some resilience vs having more resilience and higher latency.
Thanks so much! As I said, I am a noob, so didn’t realize the disadvatage of RAID 10 vs. SHR when I initially set-up. It seems to me that I have two reasonable options from what you have said. 1) add the DX unit and set it up as a second volume..which would be OK or 2) for not much more dollars, I could add a DS923+ and also have a second volume, with something like a pair of 10TB drives using SHR to make a mirrored pair. Then if at some point I needed more storage, I could add two more drives to the 923+. I,am leaning towards that option unless I am missing something.

Thanks so much for the detailed reply.
I would lean towards the new NAS too. With the expansion unit you have to have the NAS functioning to access the other unit. Then there’s more point of failure that could happen, not least two power supplies.

For a little more £££/$$$/€€€, losing a bay, you get a whole new NAS. Which can also be used as a fallback etc.

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