Over the last weekend I finally managed to setup my RaidSonic NAS-4220B. Now it runs OpenWRT ported by this guy. I only added a few kernel options (cryptoloop, md, and raid1) and added the mdadm utility (raid config utility). You probably ask why I use cryptoloop and not dm_crypt. The box has hardware acceleration for AES but this is only implemented for IPSEC and LOOPAES. So now I run LOOPAES on top of RAID1. The performance is not very good but this is due to my tests using scp to copy files to and from the NAS. I only get 1.1MB/s. CPU is maxed out on the NAS while the copy process is running. Since the box will be doing automated backups over a DSL line this is fast enough (faster than the downstream of the DSL line).
Some notes: I have two 500GB disks in the box, when I tryed to create a ext2 file system on the disk I got an out of memory error from mke2fs. This is due to the fact that the NAS-4220 really runs low on memory (10M free). The easiest fix was to hook up a USB disk and use that for swap space just until the file system is created :-)
I'm not completely done yet with the setup lets see what other surprises there are for me.