First thing esav - don't panic, you MIGHT be able to recover something but it will be hard work.
From the manual:
RAID 0 provides data striping, which spreads
out blocks of data over both drives, but does
not provide data redundancy.
Although performance is improved, the lack of
fault tolerance means that if one drive fails, all
data in the array will be lost.
Note the second paragraph - not good.
It might be that there is a problem with the DNS-323 and the disks are OK. If that is the case then you might be able to do a full recovery using another 323. If a disk has failed then you may be able to get individual files copied but that depends on where the split for the striping is and if you can recognise the files when you see them.
To try a recovery, get yourself a USB/SATA caddy or adapter. That way you can remove one of the drives and check it with a computer. You will also need an installable IFS to allow you read the linux file system format on your windows computers, you could also use a linux box if one is available.
Having got the drive and, if necessary, the IFS set up, try to see what is on it using something like explorer, on windows, or the standard file viewer on linux.
If you can see your files it is then a matter of copying them to another drive. If you can't see any files, try the other drive but you might find you have BIG problems because of your using RAID 0 as I said at the start.
I have only tried this once, without much success, was able to do full restore from backup - we then converted to RAID 1 and have not had ant real problems since - it just takes a looong time to rebuild the array with 2 TB drives.