Lots of excellent advice here and I see no reason to weigh in, but I will anyway.
What I want is a Time Capsule replacement. TC, as you all know, is not RAID, but many (most?) of us are using one as part of a comprehensive backup scheme.
Elsewhere I’ve seen some enthusiasm for using a Raspberry Pi as a TC replacement. Personally I think this is a terrible idea.
The great thing about TC: it “just works”, and it’s quiet.
I wish they’d update the Time Capsule but maybe that would be replaced by a NAS
Today’s Apple wants to lease cloud, not sell NAS or TC. They won’t even put a HD into an Apple TV - they’re all about the stream now (even if it’s just from your macOS/iOS device). And with QNAP and Synology offerings there’s not a lot Apple could offer that’s value-added by comparison, especially for such a tiny hardware niche. And since it is such a small niche they’re even less likely to consider it.
True. I thought I read though of issues of running Time Machine on a NAS like Synology?
I think I’m leaning towards a Synology to start and then if I find I want to separate my Plex stuff I can move that to unRaid and that also opens up the possibility later of using a Mac Mini for stuff as well.
It’s working fine for me. My iMac Pro alternates between backing up to my Synology and to an external USB-connected (spinning) drive.
MacBook Pro backs up over WiFi. It fails sometimes due to disconnecting (e.g. when I leave in the morning, or sleep the laptop). I don’t worry too much. I usually have a wired connection once or twice a week, and it uses that too. When the laptop is at school, it backs up to a small (1T, 2.5”) spinning drive.
I do bootable backups with Carbon Copy Cloner every couple of weeks. I need a more definite schedule for this. Backup destinations are external SSDs.
Finally, both laptop and iMac are backed up by Backblaze.
Folks here on the forum helped me think these things through. I’m grateful for their help. Unexpected consequence of getting a NAS, internet usage is through the roof
Are you using your Symbology for Time Machine?
I use a synology server for time machine, no issues so far.
Thanks @OogieM. Have you tried to restore from Time Machine on your Synology? I’ve heard this is the sticking point.
Every quarter I restore a file several times hitting both newer and older TM backups. Since I have 3 drives being used in sequence and TM restore doesn’t’ readily tell me which drive it’s from I don’t know that I’ve’ tried to restore from the Synology but a quick calculation says the probability is that I have at least once or twice. Let me go try to do that now after checking when the last NAS TM backup was.
…
OK I just verified that I can restore files from the NAS backup clear back to the end of the ones stored there with no problems.
Hopefully I have not come to the attention of Murphy by doing this. 
Now all I’m doing is saving money for my Synology 1019+! Can’t wait!
Out of curiosity, and I am not sure if you have the answers, if your Mac is screwed up. Can you do a Cmd+R and then restore the OS and data from Synology. That is what I am looking for in a Time Capsule capable backup.
Never tried a full backup. No time to test for a bit but ping me again in a couple of weeks and if I haven’t tried it I may be able to then.
Never tried with the Synology. I just tried with the Drobo (encrypted TM backup) and it became a world of pain. I just decided to not be confident into the ability to do a full restore. I might have worked. That’s why I have, and always had, a clone of my drive to restore to and TM just to do have…a time machine (restore files to previous states).
If I have a complete failure:
For something as expensive as Synology, I’d expect to be able to restore completely as if from a Time Machine. Otherwise, an external USB hard disk would be a much, much cheaper option. Of course, as others have pointed out, Synology has other use cases, but it’d be a shame if it can’t do a full restore.
Since you have multiple large drives, I would NOT recommend unraid. Stick with zfs on Linux or just use FreeNas if you would like a distro that is both free and has good extensibility to common nas features.
I have seen multiple people recommend Synology, but, if you have any Linux know how or don’t mind spending time updating or configuring your system, then you can save heaps of money building your own system using used enterprise grade hardware and FreeNas. It will easily outperform Synology in cpu, ram, writes, and reads while also coming in at a cheaper price. If you want more help don’t hesitate to reach out or visit the Homelab subreddit. I would look at a dell r310 (or r320) or r710 (or r720). Less than half the cost of a 6 bay Synology and runs circles around it in performance.
@drewthor, do you have first-hand experience that FreeNAS will function reliably as a Time Machine replacement? I ask this because, in the past, there have been indications on this forum that many NAS solutions (not FreeNAS in particular, that I can recall) do not meet that requirement.
I will let you know shortly. Samba was updated in the last year to support macos seeing samba shares as time machine backups. Many people on Reddit and other places have mentioned that no longer having to use netatalk has improved stability to the point of being reliable
I was going to set it up this week on my Debian machine running zfs on linux
How’d the setup go? Did you get it up and running successfully?