Before I buy, what speed are usb-drives on DS112j ?

[JeanC]

Hi,
I am looking for a Nas primarily for use with my 3 usb drives (total 4.5 TB)
I also have a Seagate 2TB ATA to install on it.
But my main concern is how the read/write speeds on those usb drives will be.
If I use them on a plain usb-hub on windows 7 I get a write speed of 25 MB/s.
What can I expect from the DS112j?
And can it handle 3 usb drives on a hub?

Thanks.