KNOW MORE ABOUT BACK-UP OF FILE SYSTEMS AND BACKUP OF FILE SERVER

KNOW MORE ABOUT  BACK-UP OF FILE SYSTEMS AND BACKUP OF FILE SERVER

Almost all applications store their data in file systems or in databases. Therefore, in this section we will examine the back-up of file servers (Section 7.9) and in the next section we will look more closely at that of databases (Section 7.10). The chapter concludes with organizational aspects of network back-up (Section 7.11). This section first of all discusses fundamental requirements and problems in the backup of file servers (Section 7.9.1). Then a few functions of modern file systems will be introduced that accelerate the incremental back-up of file systems (Section 7.9.2). Limitations in the back-up of NAS servers will then be discussed (Section 7.9.3). We will then introduce the Network Data Management Protocol (NDMP), a standard that helps to integrate the back-up of NAS servers into an established network back-up system

Back-up of file servers

We use the term file server to include computers with a conventional operating system such as Windows or Unix that exports part of its local file systems via a network file system or makes it accessible as service (Novell, FTP, HTTP). The descriptions in this section can be transferred to all types of computers, from user PCs through classical file servers to the web server. File servers store three types of information:

• data in the form of files;

• metadata on these files such as file name, creation date and access rights; and

• metadata on the file servers such as any authorized users and their groups, size of the individual file systems, network configuration of the file server and names, components and rights of files or directories exported over the network. Depending upon the error situation, different data and metadata must be restored. The restoring of individual files or entire file systems is relatively simple: in this case only the file contents and the metadata of the files must be restored from the back-up server to the file server. This function is performed by the back-up clients introduced in

Restoring an entire file server is more difficult. If, for example, the hardware of the file

server is irreparable and has to be fully replaced, the following steps are necessary:

1. Purchasing and setting up of appropriate replacement hardware.

2. Basic installation of the operating system including any necessary patches.

3. Restoration of the basic configuration of the file server including LAN and storage network configuration of the file server.

4. If necessary, restoration of users and groups and their rights.

5. Creation and formatting of the local file systems taking into account the necessary file system sizes.

6. Installation and configuration of the back-up client.

7. Restoration of the file systems with the aid of the network back-up system.

This procedure is very labour-intensive and time-consuming. The methods of so-called Image Restore (also known as Bare Metal Restore) accelerate the restoration of a complete computer: tools such as 'mksysb' (AIX), 'Web Flash Archive' (Solaris) or various disk image tools for Windows systems create a complete copy of a computer (image). Only a boot diskette or boot CD and an appropriate image is needed to completely restore a computer without having to work through steps 2–7 described above. Particularly advantageous is the integration of image restore in a network back-up system: to achieve this the network back-up system must generate the appropriate image. Furthermore, the boot diskette or boot CD must create a connection to the network back-up system.