I'm looking for a portable NAS solution for around 30 servers to back up to. I require 8-16TB of space. Does anyone have any experience of the Qnap TS-809 and know if it would be suitable for this many servers to be backing up to?
It should work fine - depending on your switch (if you have a managed switch that can do 802.3ad and aggregate the two ports on the Qnap) you should see a win from the dual NICs.
With any NAS backup like that your headache is going to be scheduling the backups to make sure all your clients aren't writing to it or reading from it at once. Restoring or backing more than a couple of machines simultaneously you'll just suffer...
imho, qnap is designed for soho/sme where everything with the kitchen sink is built into it. too much unnecessary services running in it. and i would not expect performance from such devices.
i would suggest build your own box and setup freenas.org or opensolaris http://sites.google.com/site/eonstorage/ using zfs + raidz2 http://blogs.oracle.com/ahl/entry/double_parity_raid_z for the storage, all these feel like almost perfect box for me.