可靠性、可用性和可維護性

可靠性、可用性和可维护性（）是電腦硬體上的術語，最初來自IBM公司為其大型主機所做的宣傳廣告，強調大型主機系統的堅韌強固。如今這個概念已廣為人知，並被簡稱為RAS。

定義
可靠性（Reliability）是指定時間 t* 內，產生正確輸出的機率。
*可用性（Availability）是指系統的運作時間，工作時間比總時間，一般用百分比表示，例如99.999%（5個9）。
*可维护性（Serviceability）是指若系統發生故障，是否可以快速檢查和維修。

參見
*高可用性
*RAMS

参考文献

• [http://labs.hoffmanlabs.com/node/95 Itanium Reliability, Availability and Serviceability (RAS) Features] Overview of RAS features in general and specific features of the Itanium processor.
• [http://www-05.ibm.com/de/events/breakfast/pdf/POWER7_RAS_Features_Feb_2012.pdf POWER7 System RAS Key Aspects of Power Systems Reliability, Availability, and Serviceability. Daniel Henderson, Jim Mitchell, and George Ahrens. February 10, 2012] Overview of RAS features in Power processors.
• [http://www.intel.com/content/www/us/en/servers/reliability-availability-and-serviceability-for-the-always-on-enterprise-paper.html Intel Corp. Reliability, Availability, and Serviceability for the Always-on Enterprise (appendix B)] and [http://www.intel.com/content/www/us/en/processors/xeon/xeon-e7-family-ras-server-paper.html Intel Xeon Processor E7 Family: supporting next generation RAS servers. White paper.] Overview of RAS features in Xeon processors.
• [http://www-01.ibm.com/support/docview.wss?uid=isg2c24bd608371def398525776100545fcb&aid=1 zEnterprise 196 System Overview. IBM Corp. (Chapter 10)] Overview of RAS features of IBM z196 processor and zEnterprise 196 server.
• [http://www.oracle.com/technetwork/server-storage/sun-sparc-enterprise/documentation/o13-026-m5-32-ras-1923495.pdf Maximizing Application Reliability and Availability with the SPARC M5-32 Server] RAS features of Oracle’s SPARC M5-32 server