RN214 ReadyNAS Disk Trays

Just so you know, the caddies from the older desktop (but not rack mount) NAS will work in your NAS (but not the other way around).  They don't have the toolless mount system (which, IMHO, is a pretty silly thing since one should not be swapping drives willy nilly) and have no provisions for a 2.5" drive (though there are adapters that will work).  The ones with the round button are a PITA to release, but again, you aren't doing that often.  I see some for sale right now on eBay.  Unfortunately, you'll find they aren't cheap.  There is no generic substitute.  They look like the mirror image of one type of Chenbro caddy, but you can't interchange them because of that reversal.