Hi again,
As far as the Dlink notifying you when the disk approaches "full", I am not sure how common this is. I haven't seen a post like yours as far as I can recollect so it may not occur that often. Just to be sure, if you can get into the 325's gui and check through the log files, it is possible that you could configure some type of email alert similar to the Smart Test, but I don't know for sure. I don't use Dlink's cameras so I don't have to worry about the hidden files issue that JavaLawyer has pointed out. I do know that some recommend never allowing a hard drive to more than 85 to 90% of it's capacity as the drive becomes increasingly sluggish and unresponsive. I have to say also, I am not an fan of Raid 1 especially when the user assumes that this functions as a "true" backup, it is not and if you google Raid 1 failures you may come to agree. You need a seperate backup and at least one local with one remote backup is highly recommended, more if data is critical or high value. JavaLawyer has a sticky regarding the limits of Raid 1 setups, worth reading
http://forums.dlink.com/index.php?topic=52519.0