Free tutors How to take Back-up of NAS servers

Free tutors How to take Back-up of NAS servers

NAS servers are preconfigured file servers; they consist of one or more internal servers, preconfigured disk capacity and usually a stripped-down or specific operating system (Section 4.2.2). NAS servers generally come with their own back-up tools. However, just like the back-up tools that come with operating systems, these tools represent an isolated solution (Section 7.1). Therefore, in the following we specifically consider the linking of the back-up of NAS servers into an existing network back-up system. The optimal situation would be if there were a back-up client for a NAS server that was adapted to suit both the peculiarities of the NAS server and also the peculiarities of the network back-up system used. Unfortunately, it is difficult to develop such a back-up client in practice:

• If the NAS server is based upon a specific operating system the manufacturers of the network back-up system sometimes lack the necessary interfaces and compilers to develop such a client. Even if the preconditions for the development of a specific back- up client were in place, it is doubtful whether the manufacturer of the network back-up system would develop a specific back-up client for all NAS servers: the necessary development cost for a new back-up client is still negligible in comparison to the testing cost that would have to be incurred for every new version of the network back-up system.

• Likewise, it is difficult for the manufacturers of NAS servers to develop such a client. The manufacturers of network back-up systems publish neither the source code nor the interfaces between back-up client and back-up server, which means that a client cannot be developed. Even if such a back-up client already exists because the NAS server is based upon on a standard operating system such as Linux, Windows or Solaris, this does not mean that customers may use this client: in order to improve the Plug&Play- capability of NAS servers, customers may only use the software that has been tested and certified by the NAS manufacturer. If the customer installs non-certified software, then he can lose support for the NAS server. Due to the testing cost, manufacturers of NAS servers may be able to support some, but certainly not all network back-up systems. Without further measures being put in place, the only possibility that remains is to back the NAS server up from a client of the NAS server (Figure 7.12). However, this approach, too, is doubtful for two reasons:

• First, this approach is only practicable for smaller quantities of data: for back-up the files of the NAS server are transferred over the LAN to the network file system client on which the back-up client runs. Only the back-up client can write the files to the back-up medium using advanced methods such as LAN-free back-up.

• Second, the back-up of metadata is difficult. If a NAS server supports the export of the local file system both via CIFS and also via NFS then the back-up client only accesses one of the two protocols on the files – the metadata of the other protocol is lost. NAS servers would thus have to store their metadata in special files so that the network back-up system can back these up. There then remains the question of the cost for the restoring of a NAS server or a file system. The metadata of NAS servers and files has to be re-extracted from these files. It is dubious whether network back-up systems can automatically initiate this process. As a last resort for the integration of NAS servers and network back-up systems, there remains only the standardization of the interfaces between the NAS server and the network back-up system. This would mean that manufacturers of NAS servers would only have to develop and test one back-up client that supports precisely this interface. The back-up systems of various manufacturers could then back up the NAS server via this interface. In such an approach the extensively of this interface determines how well the back-up of NAS servers can be linked into a network back-up system. The next section introduces a standard for such an interface – the Network Data Management Protocol (NDMP).