Distributed system is a collection of independent systems which can communicate with each other by transferring massages. There are some major issues in distributed systems but we focus in this paper on fault tolerance. It is the system’s ability to work in the condition when there occur any type of some fault in the system, like failure in communication, hardware or resources. It is a very important issue in distributed system, in this paper we present a survey of different types of fault tolerance techniques and their comparison.
METATOYs are optical components that can produce light ray fields that were thought to have been forbidden until now. They can be utilised to produce effects that were thought to be science-fiction. Invisibility cloaks, but on a larger scale than previously possible, is the major one as well other abstract effects to light rays. This report will explore what happens when two dove prism arrays are brought together and rotated and how they can produce these supposed illegal light ray fields.