Because, just like RAID 1 any infection or loss will be copied to the mirror. That said, if I feel like a sync I use a few titles. All seem fine and I've used them without thinking which is best. List follows.
Roadkil's Unstoppable Copier.
GoldSync.
SyncBack.
Bob
Hi I was just wondering if anyone knew how to mirror a folder on a desktop on to a D Link 320L NAS hard drive. What I mean by mirror is that they would be exactly the same. For example, one folder I was going to do was Movies and I was hoping that I could back it up on the NAS and when ever I moved a movie or deleted one then the same would happen on the other. Even if I could have it that the NAS only copied the original on the desktop then I would be happy. Any help or links to tutorials would be much appreciated.
Also does anyone know if I could get my Samsung smart TV to detect the NAS hard drive? I am currently using an Android TV device but would like to cut that out.
Thank you for your time and hopefully I can get this sorted and maybe I will sleep better

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic