Backup and Reliability Requirements

Backup and Reliability Requirements
One of the most powerful characteristics of Windows NT Server is its reliability. Windows NT Server includes the following reliability and fault-tolerance capabilities:
Automatic restart
Complete tape backup support
Error handling and protected subsystems
Fault tolerance using disk mirroring, disk duplexing, and disk striping with parity (RAID 5)
Recoverable file system, automatic replication of directory partitions, and support for Backup Directory Servers
Uninterruptible power supply (UPS) support
The following sections define hardware requirements and recommendations for peripheral devices that support reliability and availability under Windows NT Server.
Backup Hardware
This section defines the requirements for backup hardware for servers.
178 System includes integrated backup solution
An integrated tape drive or other device is a recommended inclusion in the system. Although the recommended method to back up files on another server is to use a backup service under Windows NT Server, system administrators will commonly want offline backup capabilities to be available.
For information about hardware requirements related to backup capabilities, such as tape drives and so on, see Chapter 5, “Basic Storage Device Requirements.”
Power Supply
This section defines the guaranteed power requirements for servers.
179 System includes UPS provided with system
For servers deployed in many corporate environments, the more common choice will be to provide guaranteed power for the server room.
180 System includes power supply protection using N+1 (extra unit)
The system overvoltage/undervoltage protection and power supply switch-over circuitry should have the capability to regulate according to the system load. For each voltage used in the system, the output voltages of the redundant power supplies should be within the range of values that can guarantee the proper operation of the system, no matter which supply is active. Power-supply switch-over should occur swiftly enough to maintain normal server system operation.
181 System supports replacement of power supplies
Recommended: Hot-swapping capabilities for power supply replacement and power supply redundancy.
Fault-Tolerant Hardware
This section provides design guidelines for fault-tolerance features and capabilities.
182 System includes multiple hard drives
Recommended: Hot-swappable drives.
Bus mastering is required for the drive controllers. Use of multiple hard drives and controllers in a server system provides both performance and reliability benefits, and it is strongly recommended for server systems.
For information about hardware requirements related to Windows NT clustering, see Appendix A, “Clustering Hardware,” in this guide.
183 System includes intelligent RAID controller with adequate storage capacity
An intelligent RAID controller, where the controller itself has the capability to run the array management software locally rather than simply executing disk accesses for host-based array software, provides the benefit of reduced demands on the host processor or processors, thereby freeing those computing resources and allowing their use by other tasks.
If an intelligent RAID controller is provided in a system, it should be capable of handling sufficient amounts of disk storage to fulfill the needs of the targeted usage model for that server. These needs will vary based on the storage-intensive nature of the server’s tasks.
184 System supports at least one of RAID 1, 5, or 1/0
RAID 1 and RAID 1/0 are recommended. RAID 5 is also acceptable. RAID 0 (for enhanced performance but no added reliability) is optional.
185 RAID support includes notification of failed drive
If RAID support is implemented, notification of a failed drive must be provided by the disk subsystem, with notification sent to the system administrator.
186 RAID subsystem supports automatic replacement of failed drive
The RAID subsystem must provide automatic replacement of a failed drive by a standby disk and must rebuild lost data without interfering with system operations.
187 RAID subsystem supports manual replacement of failed drive
The RAID subsystem should provide for manual replacement of a failed drive without shutting down the system. The subsystem should also rebuild lost data without interfering with system operations.
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