NDMP(1)
It has been a decade since the first version of the Network Data Management Protocol was launched as an effort to solve the problems posed by the backup and recovery of network file servers. Initial work on the standard was spearheaded by Intelliguard Software (subsequently rolled into Legato Software and EMC Corp.), which produced storage management software, and Network Appliance Inc., which manufactures network file servers.
The standard was developed to address the fact that network file servers are not able to use the storage device drivers designed for general-purpose computers. They are specialized appliances that connect to a network and are optimized to perform a single set of tasks. Their files are usually mounted by general-purpose computers through protocols such as the Unix/Linux Network File System and Microsoft Windows Common Internet File System.
Without NDMP, there were two choices for backing up network file servers. One was to mount their file systems onto the file system of a computer across the network and do the backup there. The downside was that backup and restore required network and server bandwidth. Moreover, the added complexity made it difficult to use optimized aspects of the network file server, such as Network Appliance’s Snapshot capability.
The other option was to write driver software for each type of network file server and locally attached storage system (tape drives, jukeboxes, CD-ROM writers). That required vendors (manufacturers of network file systems and storage systems and/or backup control software houses) to produce multiple driver variants.
The advantage of NDMP is that it establishes a single set of interfaces between the three components involved in a backup or restore operation——the software controlling the backup or restore, the source medium and the destination medium. When all the components are NDMP-compliant, the manufacturer of each can concentrate on maximizing the efficiency of its side of the interface.
By 1999, the time for backing up an Oracle database residing on one of Network Appliance’s network file servers had been reduced from hours to minutes. Instead of mounting the network file server’s files to the computer acting as an Oracle server, the backup was done locally on the network file server and used Network Appliance’s Snapshot files, which allow for live backup of a consistent disk image.
The paradigm for NDMP is a client/server architecture in which data producers and consumers are thought of as servers or service providers, and the backup control software is thought of as a client. There is one client per NDMP session. There can be multiple servers. In NDMP documentation, clients are also sometimes called data management applications, and servers or service providers are called data service providers (DSP).
A DSP such as a network file server produces a data stream when it provides data to a storage system for backup. It consumes data when a storage system provides it with data for a restore. (To Be Continued)
翻譯： 虛網(wǎng)絡(luò )數據管理協(xié)議(1)
網(wǎng)絡(luò )數據管理協(xié)議第一版問(wèn)世以來(lái)已有十年了，它是為解決因服務(wù)文件服務(wù)器的備份和恢復帶來(lái)的問(wèn)題而開(kāi)發(fā)的。最初是由Intellguard軟件公司（后來(lái)它合并到了Legato軟件和EMC公司）和Network Appliance公司率先進(jìn)行此標準的研究，前者提供存儲管理軟件，而后者制造網(wǎng)絡(luò )文件服務(wù)器。
此標準的開(kāi)發(fā)是針對這樣一個(gè)事實(shí)，即網(wǎng)絡(luò )文件服務(wù)器不能使用為通用計算機設計的存儲設備驅動(dòng)程序。它們是聯(lián)在網(wǎng)絡(luò )上的專(zhuān)用設備，為完成一組單一的任務(wù)而進(jìn)行了優(yōu)化。通常，其文件是由通用計算機通過(guò)諸如Unix/Linux網(wǎng)絡(luò )文件系統和微軟的視窗公共互聯(lián)網(wǎng)文件系統安裝的。
不用NDMP，備份網(wǎng)絡(luò )文件服務(wù)器有兩種選擇。一是將網(wǎng)絡(luò )文件服務(wù)器的文件系統通過(guò)網(wǎng)絡(luò )裝入一臺計算機的文件系統，在這臺計算機上進(jìn)行備份。其缺陷是備份和恢復需要消耗網(wǎng)絡(luò )和服務(wù)器的帶寬。而且，增加的復雜度使利用網(wǎng)絡(luò )文件服務(wù)器的優(yōu)化功能很困難，如Network Appliance公司的“快照”功能。
另一個(gè)選擇為每一類(lèi)型的網(wǎng)絡(luò )文件服務(wù)器編寫(xiě)驅動(dòng)程序，本地聯(lián)到存儲系統（磁帶機、光盤(pán)庫機和CD-ROM刻錄機）。這需要廠(chǎng)家（網(wǎng)絡(luò )文件系統和存儲系統的制造商和/或備份控制軟件公司）生產(chǎn)多個(gè)驅動(dòng)程序。
NDMP的優(yōu)點(diǎn)就是在備份或恢復操作中涉及的三樣東西（控制備份或恢復的軟件、源介質(zhì)和目的介質(zhì)）之間建立一組單一的接口。當這些東西都符合NDMP時(shí)，每樣東西的制造商就能集中精力最大程度地提高接口里面的效率。
到1999年，常駐在Network Appliance公司的網(wǎng)絡(luò )文件服務(wù)器上的Oracle數據庫備份所需時(shí)間從幾個(gè)小時(shí)縮至幾分鐘。而且備份是本地在網(wǎng)絡(luò )文件服務(wù)器上利用Network Appliance公司的“快照”功能完成的，而不是將網(wǎng)絡(luò )文件服務(wù)器的文件裝到起著(zhù)Oracle數據庫服務(wù)器的計算機上，這就允許實(shí)現一致的磁盤(pán)圖像的實(shí)況備份。
NDMP模式是一種客戶(hù)/服務(wù)器架構，其中數據生產(chǎn)者和消費者被認為是服務(wù)器或服務(wù)提供者，而備份控制軟件被認為是一個(gè)客戶(hù)。每一次NDMP會(huì )話(huà)只有一個(gè)客戶(hù)，但可以有多個(gè)服務(wù)器。在NDMP的文檔中，客戶(hù)有時(shí)也叫做數據管理應用，服務(wù)器或服務(wù)提供商叫做數據服務(wù)提供者（DSP）。
當DSP，如網(wǎng)絡(luò )文件服務(wù)器，給存儲系統提供用做備份的數據時(shí)，生成一個(gè)數據流。當存儲系統給DSP提供恢復用的數據時(shí)，DSP消費數據。（未完待續）
