Know more on LAN-free back-up ,LAN-free back-up with shared disk file systems

Know more on  LAN-free back-up and  LAN-free back-up with shared disk file systems

LAN-free back-up dispenses with the necessity for the 3rd-Party SCSI Copy Command by realizing comparable functions within the back-up client

back-up, metadata is sent via the LAN. File contents, however, no longer go through the  back-up server: for back-up the back-up client loads the data from the hard disk into the main memory via the appropriate buses and from there writes it directly to the back-up medium via the buses and the storage network. To this end, the back-up client must be able to access the back-up server's back-up medium over the storage network. Furthermore,

back-up server and back-up client must synchronize their access to common devices. This is easier to realize than server-free back-up and thus well proven in production environments. In LAN-free back-up the load on the buses of the back-up server is reduced but not the load on those of the back-up client. This can impact upon other applications (databases, file and web servers) that run on the back-up client at the same time as the back-up.

LAN-free back-up is already being used in production environments. However, the manufacturers of network back-up systems only support LAN-free back-up for certain applications (databases, file systems, e-mail systems), with not every application being supported on every operating system. Anyone wanting to use LAN-free back-up at the moment must take note of the manufacturer's support matrix (see Section 3.4.6). It can be assumed that in the course of the next one to two years the number of the applications and operating systems supported will increase significantly.

 LAN-free back-up with shared disk file systems

Anyone wishing to back up a file system now for which LAN-free back-up is not supported can sometimes use shared disk file systems to rectify this situation (Figure 7.9). Shared disk file systems are installed upon several computers. Access to data is synchronized over the LAN; the individual file accesses, on the other hand, take place directly over the storage network (Section 4.3). For back-up the shared disk file system is installed on the file server and the back-up server. The prerequisite for this is that a shared disk file system is available that supports the operating systems of back-up client and back-up server. The back-up client is then started on the same computer on which the back-up

server runs, so that back-up client and back-up server can exchange the data via Shared Memory (Unix) or Named Pipe or TCP/IP Loopback (Windows). In LAN-free back-up using a shared disk file system, the performance of the back- up server must be critically examined. All data still has to be passed through the buses of the back-up server; in addition, the back-up client and the shared disk file system run on this machine. LAN data traffic is no longer necessary within the network back- up system; however, the shared disk file system now requires LAN data traffic for the

synchronization of simultaneous data accesses. The data traffic for the synchronization of the shared disk file system is, however, comparatively light. At the end of the day, you have to measure whether back-up with a shared disk file system increases performance for each individual case.

Although the performance of LAN-free back-up with the aid of a shared disk file system is not as good as the performance of pure LAN-free back-up, it can be significantly better than that of back-up over the LAN. Therefore, this approach has proved its worth in  production environments, so that it can be viewed as an interesting transitional solution until LAN-free (or even server-free) back-up becomes available.