Servers are fully built, tested & delivered free anywhere in the UK & Europe.
Shortage of memory is the most common reason for a system slowing down. With Windows 10 your system will barely stagger along with 4 GB. It will work steadily with 8GB but ideally you should go for 16GB. Gaming & CAD will run fine with 16 GB but 32 GB will future proof the PC.
Raid 1 provides fault tolerance from disk errors and failure of all but one of the drives. Increased read performance occurs when using a multi-threaded operating system that supports split seeks. Array continues to operate so long as at least one drive is functioning.
If one hard drive fails the 2nd hard drive will continue running without loss of data, the faulty drive can be replaced and the array will be rebuilt.
Raid 0 provides improved performance and additional storage but no fault tolerance, both drives are linked to make one big drive giving much better performance than a standard single drive.