But these aren't just NAS systems -- the DS509+ can also serve to iTunes, connect an external USB disk for scheduled backups, act as an rsync source or destination (including scheduled rsync backups to another device, Synology or not), provide a simple and fully configurable BitTorrent client, and even drive USB speakers. In fact, the only functions that I find lacking in the DS509+ is Time Machine support for backing up Macs via the network and iSCSI support. These are functions that some competing products like the NetGear ReadyNAS do offer, but if you don't need them, Synology's interface more than makes up for it. I've asked Synology when these capabilities might be added, and it appears that they're on the road map, hopefully available by August of 2009. Of course, my brand-new Apple Airport Express with simultaneous dual-band support apparently can't properly function as a Time Machine destination either, even though it's supposed to, but that's a story for another time.
As far as the hardware, the DS509+ runs five internal drives via software RAID, with hot-swap capabilities, and leverages the expansion unit as a single entity -- that is, while you can combine the two arrays into a single volume, they're handled as unique RAID sets. Filled with 2TB drives, these two small boxes can take 20TB raw and use the dual gigabit NICs -- separately or bonded -- to connect all that storage to the network. Not bad at all for a device that starts at $899. And expanding the storage can be done on the fly with no data loss.
Performance is very good, but not in the realm of high-end NAS devices. Across a five-disk RAID5 array, I can pull roughly 53MBps sequential reads and 35MBps sequential writes across NFS using random file sizes. That's very respectable for the price. SMB performance is slightly slower. Also, speaking of SMB, the DS509+ can attach to an Active Directory domain for authentication and share security.
All told, I continue to be impressed with Synology's hardware and its commitment to open source and providing an open platform. One of my major problems with smaller NAS systems is that you're generally locked into their (sometimes) terrible Web management interface, and there's absolutely no option to color outside the lines if needed. The Synology boxes are not that way -- they manage to make easy things easy, and hard things possible, which is the holy grail of just about everything in IT.