With Raid 0, you have a better performance since the data is written across 2 disks, if any of the 2 disks dies, your data is lost since a part of the data is one disk and the other on on the other disk.
With Raid 1, you have a slight performance impact because you are always mirroring data that is on one disk to the other disk. If one disk dies, however, the other disk contains all the data necessary.
With My Cloud, you have 3 models. My Cloud comes with one disk, but the possibility to mirror the content to an attached USB disk, You also have My Cloud Mirror that comes preconfigured as Raid1, but you can change to Raid0. My Cloud EX2 similarly. The difference between EX2 and My Cloud Mirror comes down to some relatively minor hardware differences. EX2 is positioned as a more advanced, faster box, with more features.
You have no content stored on WD Servers. Those are only used to track where your NAS is on the Internet, and, depending on your configuration by design, sees the content flowing there or not. You have 2 backups. One is Smarware or other backup software backing up the content of your PC to the NAS. One is Safepoint, mirroring (no file retention) the content of the NAS to an attached USB disk, and/or RAID1 mirroring with the Mirror version set up as Raid1
Remote access to the My CLoud is possible also directly, without the WD services involved in seeing your data, or seeing your NAS, but this requires some basic and networking skills to set up. So WD services make it easier for the consumer.
There is no copy on the WD servers.
Sometimes the WD servers are down yes. Probably something temporars as the services grow and bugs are squashed.
The main difference between MyCloud and MyBook is that the first one is a small networked computer with a big disk sharing its disk on your network (you cannot connect this disk to a computer using USB), while the MyBook live is a USB disk with some advanced features, including sharing content over the network through your computer. My Cloud is accessible when you computer is down. MyBook is not.
On the right network configuration, the MyCloud read/write performance is close but lower than USB3.0 (about 60MB/s)
Different products for different use cases.
MyCloud series are great products, but you need a good network setup to see high performance. If performance to the disk is paramount, go for a USB 3.0 disk. If always on access is more important, go for the MyCloud, knowing that your performance will be most likely limited but your network bandwidth. Gigabit connections and switch/router removes network bandwidth issues.
