IP系统基础知识＿技术.ppt

* * * * * 存储涉及3个基本元素：介质，链路，文件系统。 * * 关于介质的特性还应该了解： 介质容易出错，但大多数设备采用了某种补偿办法。 介质容易受腐蚀，即使光介质也不例外。 灰尘和潮湿是介质的致命敌人。 所有的介质都有一定的失效期，甚至在最优的条件下也不例外。 * 企业数据是企业的命脉，必须要妥当，安全地保存。而在要存取时，能快速地有效地提供与用户。因此对数据存储的可靠性，数据使用的可用性，及数据备份的保存与复原要求越来越高。 从另一个角度来了解存储系统的重要性是灾备。数据中心因事被毁后，所有硬件都能用钱重新购买，但数据假如同时被毁，这个企业可能便无法生存了。 * * For reference, consider the architecture for direct-attached storage: The “wiring” is direct attachment between the server and the storage device, so that no other device on the network can have access to the stored data without going through the server. The file system resides on the server. * NAS allows the storage device to connect directly to the network. The “wiring” is direct attachment to the local area network, which means there is no sever between the data and any other device on the network. The file system now resides on the NAS itself. This is essentially a thin server with a special operating system optimized to provide access at the file level. Although NAS solves the problem of data being isolated behind servers, to still relies on the client/server network for all communication and data transport, which creates an overhead burden on that network. NAS systems are simplified to address specific needs as quickly as possible-in real time. NAS devices are well suited to serve networks that have a mix of clients, servers, and operations and may handle such tasks as corporate file serving, serving Web pages, audio-video streaming and tape backup. NAS appliances can range from workgroup level, which can be as inexpensive as $800, to the enterprise level, priced in excess of $100,000. While NAS sounds simple, it can actually be an elegant design that can include many advanced features and functionality, such as support for multiple operating systems, disaster recovery, high capacity and clustering. NAS transports data at the file level, via transports, such as Ethernet using IP. NAS uses different formats, depending on the environment in which it is installed