@gogo_jiro just to address a few of your points...
UPS is useful to protect both the hardware but also data integrity in the case that it happens when writing the same data to the two disks. My latest power outage was last week when some building developers cut a big cable nearby, we're not in the back of beyond and still manage to get a few a year.
In Storage Manager each disk has an option which would be wise to keep disabled when there's no UPS.
Two disks may be all you need, using SHR / RAID 1 to mirror the drives. It's possible to expand by switching out disks with bigger ones. My comment was to just consider if you might see a time where more storage would be needed, such as if you decide to host a video library. Now is the ideal time to think about it.
For basic file serving you can even connect USB drives to the NAS and use them via SMB, etc. But for some of the NAS packages, e.g. Active Backup for Business, then you have to use internal storage on a Btrfs volume. The NAS doesn't support Btrfs formatted external drives.
Backup of the NAS can be as simple as connecting a suitably large USB drive and running Hyper Backup. Though it also supports rsync/WebDAV server and cloud destinations (though not OneDrive, much to a lot of complaining on the o
ther forum). Multiple tasks to different destinations are supported. This backs up the NAS and package configurations (as much as is supported and better in DSM 7), and shared folders and their data.
If I can pull this back to summarise the salient features of the in-scope NAS, even the oddly spec'ed and priced
DS420+.
The
DS220+ is a nice home server if a dual core CPU will suffice. But VM's when running will require cores to be assigned. The 4-bay version, DS420+, is only slightly cheaper than the
DS920+ so why wouldn't you just get that if you need 4-bays?
The
DS720+ is a really nice home server, so the question of this vs DS920+ is 'is it worth spending another ~£100* now?'. That £100 only gets you 2GB of RAM, if you only need two bays. But if you later need 8TB then your options are:
- DS720+ buy two 8TB drives at ~£400 and put the two 4TB on a shelf, or securely scrub them and resell.
- DS920+ add a third 4TB for ~£100.
*Change to your currency unit.
The hard bit is knowing in advance how much you're going to find to do with the NAS that you hadn't thought of before buying it... or, alternatively, not find. To be totally honest, other than for running VMM, you'll probably be really happy with any of these.
| Feature | DS220+ | DS720+ | DS420+ | DS920+ |
|---|
| Internal drive bays | 2 | 2 | 4 | 4 |
Supports DX517
(eSata port) | No | Yes | No | Yes |
| CPU | Dual core
Intel Celeron J4025 | Quad core
Intel Celeron J4125 | Dual core
Intel Celeron J4025 | Quad core
Intel Celeron J4125 |
| RAM (included (soldered to PCB)) | 2 GB | 2 GB | 2 GB | 4 GB |
| RAM (max (soldered + one slot)) | 6 GB | 6 GB | 6 GB | 8 GB |
SSD read/write cache
(2x M.2 Drive Slots) | No | Yes | Yes | Yes |
| 1 GbE LAN ports | 2 | 2 | 2 | 2 |
| Warranty | 2 years | 3 years | 3 years | 3 years |
