High-availability server solution for Linux

Article Title: high-availability server solution for Linux. Linux is a technology channel of the IT lab in China. Includes basic categories such as desktop applications, Linux system management, kernel research, embedded systems, and open source.
In today's society, it is essential for modern enterprises to use computer systems to provide timely and reliable information and services. However, the availability of information systems is usually affected by the following two situations: first, computer hardware and software will inevitably fail. these faults may cause great losses to the enterprise, and even lead to the termination of the entire service and system paralysis. Secondly, due to system maintenance and upgrade, A normal shutdown caused by the installation of new hardware or software may also cause the application to stop. It can be seen that for enterprises or companies that need to provide application services without interruption, the high availability of the system is particularly important. Therefore, appropriate measures must be taken to ensure that computer systems provide uninterrupted services to fully ensure system availability.
Mid-soft Linux high-availability servers play an important role in industries with high availability requirements. For modern enterprises, timely and reliable information services are necessary, but faults in software and hardware are inevitable. In some key fields, their basic business features are strong real-time performance, the transaction service cannot be stopped because of the large amount of instantaneous data streams. In the event of server downtime or data loss, both reputational and economic losses will occur. In order to reduce the unnecessary losses caused by faults, the high-availability server of the soft Linux system provides efficient and uninterrupted protection to ensure the stable and uninterrupted operation of the business system.
In the high-availability server of Linux, any application service can run on any node in the cluster system. When a node fails, all the protected services running on the node will be migrated to other nodes according to the predefined rules, to fully guarantee the application system access continuity in the case of various faults.
Features of mid-soft Linux high-availability servers:
■ High Availability
To achieve high availability of Linux systems connected together in a cluster, by monitoring the health status of the system and applications, maintain customer connectivity and provide uninterrupted data access to any customer, regardless of the Internet, Intranet, or Internet. When the system goes down, the applications on the cluster can be automatically switched to another server in the cluster, minimizing the loss of single point of failure, in this way, an error-tolerant environment is created in Linux to meet the strict availability requirements for key task operations.
■ Proactive protection
Failure of a hardware component or application can be detected by multiple error detection mechanisms in advance, instead of waiting until the system is completely invalid. Use smart processes and multiple LAN heartbeats to connect to the monitoring cluster. The System and Application health status are determined by regularly sending additional signals between the two server nodes. The system status is confirmed before the action is taken, which reduces the risk of single point of failure, minimize the number of errors. When the application fails but the hardware still works normally, only the failed application is restored and not completely restored to the other server. This restricts unnecessary switching.
■ Transparent failover
If server availability is interrupted due to an event, the protected resources and applications are automatically transferred to another server in the cluster. Because the switchover is transparent to the client, failure of a single system does not affect users' work. Migrating all applications and transferring connectivity enables users to continuously access applications and data. This ensures that all customers are not affected by system failures.
■ Scalability
You can simply add nodes to the cluster so that the application can support more users. It also supports scalability at the application level to ensure the availability of failure protection. When multiple (multidireal Al) configurations are installed, invalid applications on a computer can be restored to individual machines.
■ Data Access and integrity
When running in a shared storage environment, data storage is separated from services in the cluster. All data is stored in a shared disk array. This independence allows you to store data without having to consider the application on the host. In addition, the shared storage locking mechanism allows only one application to access at any time by locking the drive, maintaining data integrity.
■ Recovery operation
Mid-soft Linux high-availability servers support disaster tolerance and multi-system failure recovery, including:
(1) multi-direction recovery
Supports a four-node cluster with multi-direction failover configuration. The two nodes are connected to the same shared disk.
(2) failover
Cascading failure switching between up to 32 active nodes is allowed to ensure continuous access by the customer in the event of system or application failure.
(3) shared data support
Supports N + 1 configuration. Each shared SCSI bus supports up to two nodes. This allows application recovery based on shared SCSI disks between two nodes connected to the same shared disk in the cluster. In this configuration, there is a server that plays an Active/Active role and provides failover for any other node in the cluster.
■ Application Recovery Toolkit
Provides application Recovery kits for commercial software, including databases, Web servers, and application servers. These application Recovery kits provide tools to manage and control a specific application. After the recovery toolkit for a specific application is installed, You can monitor the health status of the application and automatically restore the application when it fails. At the same time, the application recovery software development kit (SDK) is also provided to support the development of specific application Recovery kits. The application Recovery SDK provides a powerful framework for developing custom recovery routines for specialized applications and commercial application servers. Special recovery routines can be defined by writing application Recovery scripts directly.
■ Online maintenance and upgrade
It is allowed to keep the system running during scheduled downtime maintenance or upgrade and when the system fails or the application stops responding. The ability of Medium-soft high-availability servers to defend against errors brings great convenience to system or application upgrades. Generally, the downtime of routine maintenance or upgrade can be greatly reduced or even eliminated.
Working mode of high-availability servers in Linux:
1. Hot standby mode:
Working principle: the host is working, and the slave is in monitoring preparation. When the host goes down, the slave takes over all the work of the host. After the host resumes normal operation, the service is automatically or manually switched to the host according to user settings, data Consistency is solved through a shared storage system.
2. Dual-host mutual standby mode:
Working principle: the two hosts run their respective services at the same time and monitor each other. when either of them goes down, the other host immediately takes over all of its work, ensure the normal operation of the business system. Key data of the application service system is stored in the common storage system.
3. Mutual backup mode of clusters:
Working principle: multiple hosts work together, each running one or several services, each defining one or more backup hosts for the service. When a host fails, services running on them can be taken over by other hosts.
Technical Specifications
1. system requirements:
Operating System: Soft Linux Server version
Script environment: perl5.00503 or above; Korn Shell
TCP/IP network
Minimum Memory: 32 MB
2. Host Requirements:
Any Intel-Based Server
3. shared storage options
Any NAS device
Light Channel Adapter, such as Qlogic
SCSI adapters, such as Adaptec Products
Support for SCSI-2 Reservations, Inquiry, and TestUnitReady commands
The Controller provides two I/O Ports.
Supported by standard SCSI-driven Linux SCSI
4. Disk Space Requirements:
About 10 MB of storage space in/opt
/The storage space is about 25 kb.
Supported Applications
1. database:
DB2 WE/EE/EEE,
Informix DynamicServer,
Loutus Domino, MySQL,
Oracle 8i, 9i,
PostgreSQL
2. Web Server:
Apache WebServer,
Apache/SSL (secureweb)
3. Other applications and services:
Sendmail 8.9/SAMS
SAPR/3, SAMBA,
NFS Server, Print Services,
Application with Disk Partition,
Application with File System,
File System, IP Failover,
IP Local NIC Recovery,
NAS Recovery