This site here has got quite a collection of stuffs for DNS-323.
For example module for usb-storage which allows you to plug in a usb harddisk or usb thumbdrive to use it locally. Of cos you would need to do the manual mount after plugging in and do umount if you wish to remove the device from the usb port.
For example mounting of a usb disk, download usb-storage.ko from the site to /mnt/HD_a2/lnx_bin/drivers such that the path to usb-storage.ko is
To mount the device (assuming you have only for one harddisk in the NAS)
/ # insmod /mnt/HD_a2/lnx_bin/drivers/usb-storage.ko
/ # mount -t vfat -o umask=0222 /dev/sdb1 /mnt/HD_a2/USB
The usb disk will be mounted in the /mnt/HD_a2/USB directory. To unmount and remove the module, simple do the following
/ # umount /dev/sdb1
/ # rmmod usb-storage