A fault-tolerant server is a server designed to increase system availability and stability. Fault tolerance refers to the ability of a system to continue running without interrupting service in the face of hardware failures, software errors, or other unexpected situations. Here are some key features and common techniques for fault-tolerant servers:

　　Redundant hardware:

　　Fault-tolerant servers typically contain redundant hardware components such as redundant power supplies, redundant fans, and redundant hard drives. This design ensures that even if one of the hardware components fails, the server can still continue to function.

　　Dual-machine hot standby:

　　Dual-machine hot backup is a fault-tolerant technology that usually includes two identical servers, one of which serves as the main server and the other as the backup server. If the primary server fails, the backup server can immediately take over the service, ensuring system continuity.

　　Failover:

　　Fault-tolerant servers usually have failover mechanisms that can automatically transfer services from a failed server to a functioning server. This can be achieved by using clustering technology and automation tools.

　　Hardware monitoring:

　　The fault-tolerant server will monitor the hardware status in real time through the hardware monitoring system. If any problems are detected, the system can take action, such as automatically switching to backup hardware.

　　Software fault tolerance:

　　In addition to hardware fault tolerance, fault-tolerant servers can also improve system reliability through software means. This may include implementing data redundancy, error detection and correction, and application-level fault tolerance mechanisms.

　　Disaster recovery:

　　Fault-tolerant servers are often used in conjunction with disaster recovery plans. This includes backing up data to a remote location to enable rapid recovery in the event of a catastrophic event.

　　High availability cluster:

　　Fault-tolerant servers are usually organized into high-availability clusters. Multiple servers in a cluster work together to ensure that the entire system remains available even in the event of a failure.

　　Real-time operating system:

　　Some fault-tolerant servers may use a real-time operating system to ensure that the system's response time to events is very short, thereby reducing downtime due to failures.

　　Generally speaking, fault-tolerant servers are designed to minimize the impact of system failures and ensure that the system can continue to provide services. This is particularly important for business-critical applications and systems with high availability requirements.