I have OMV running on a QNAP TS-451 and it works well. I did upgrade the flash memory on the motherboard to 8 GB and the ram to 8 GB as well. You don't have to upgrade the ram but it helps. You can't install OMV on the 512mb flash memory but you could plug a flash drive into one of the usb ports. After that, the device is almost the same as any intel system.
how do you install OMV on qnap? any guide?
i want to do this for a ts-509 Pro because it's EOL and no longer any security patches provided.