Just to drop back into the thread (although given the turn it's taken, I'm a bit hesitant!).
I ended up choosing the Drobo 5N over the Synology DS1512+. What it came down to for me was the Drobo 5N offered features I actually needed, whereas the Synology offered a huge number of features that I didn't need.
The Drobo's strengths by far are simplicity:
Volume expansion both up and down. Switch between single and dual drive redundancy as needed.
SSD cache to smooth out I/O from multiple clients at once.
No drive caddies.
Simple management.
Phone support has been outstanding in my experience, and that includes swapping out a lemon FS a couple years back.
Sometimes the Drobo 5N veers into being too simple - although the drive status in Dashboard 2.4 is more granular and informative, I still can't see drive temperatures or SMART data. I still can't get SNMP data to monitor throughput and connections. Protocol support is pretty limited - AFP and SMB only (no NFS for Linux, no WebDAV for iOS, iSCSI is a pro-only feature). DroboApps are still being redeveloped to be user friendly, but at least FS users keep their existing apps and support. Drobo's strengths are seamless storage, and they continue to deliver those basics well, with performance that's up to modern standards (I'm able to write at up to 860Mbps - and that's without jumbo frames!).
On paper the Synology seems does everything. It supports every protocol you can throw at it. It has a decent ecosystem of apps - mostly developed by Synology - to run a VPN, download data, and serve media. It has SSH built-in with all that entails. It has two connections for link aggregation and even higher speeds. You can chain on expansion units for up to 15 drives. Sounds great! And it probably is... just not for me.
For me it's mostly theoretical (your needs may vary):
I have a home server that takes care of all VPN, DNS, web, etc. and doubles as a home theater PC, so the media and server apps don't appeal.
My switch doesn't support link aggregation, and even if it did, I rarely need the raw throughput.
I don't need the ability to expand to more drive units, nor do I expect to for the life of the unit.
The USB ports for direct data backup might be handy - but as a Mac user the formatting restrictions on such drives (NTFS only) makes it less useful.
So there you have it. I want a device that lets me upgrade and change storage seamlessly, and Drobo still has the edge over Synology there. The performance of the 5N may not match the Synology on paper, but for me they may as well be matched. I'm going to benefit far more from the SSD tiering than I would from link aggregation. Other folks will have a greater need for the Synology apps, the expansion possibilities, or raw throughput - just not me.
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