In general there are different categories of faults and they are classified based on the level of severity and complexity. Faults can be categorized in to two important types based on time to recover and they are transient or permanent and in general these transient faults are simple in simple in nature and can be recovered without any special steps from the fault tolerant systems.

Permanent failures are the failures which cause a long term impact on the systems and permanent in nature and the main advantage with these types of failures is that they are easy to be identified and rectified by the fault tolerant systems . Faults can be categorized based on the actual cause for the failures and this classification covers various types of the faults like design failures.

In general these design failures are mainly caused due to design errors at the design phase itself and most of the fault tolerant systems considers these design faults as inevitable in nature and follows the required strategies to implement the fault tolerant systems. Operational failures are caused due to the lifetime failures of the system like disk crash or processor failures. Apart from these classifications following are the important types of the faults that are identified across the fault tolerance systems. 

Timing faults: These faults are occurred when the required service is not completed within the time as defined.

Omission failures: These failures are occurred due to preferment stopping of a particular service across the system.

Crash faults: These faults are occurred due to some hardware crashes across the system like disk failures or processor crashes . 

Based on these categories, the level of impact of these faults is identified on the system and the corresponding fault tolerant systems are developed based on the impact of these models. Among various fault tolerant systems discussed across the literature, fault tolerant systems for distributed systems has a wide role play and there is a lot of research done against this. There are different types of faults that were identified across the distributed systems and few of them are as listed below.

This paper is written and submitted by sai