This invention relates in general to data backup systems and in particular, to a system for storing data in one or more backup tape devices.
In many distributed computer environments such as the personal computer local area networks (PC LANs), it is necessary to record data as backup. This is crucial, for example, in certain networks such as in networks for recording airline reservations.
Network backup applications, like other types of data management, is faced with new challenges in distributed environments such as PC LANs.
Because data is often distributed among many nodes on a net, backup performance has been a real problem. In fact, none of the current strategies have significantly reduced "network overhead." However, this invention introduces a new technology which provides a very elegant solution to the apparent complexity of distributed data management. Discussed below are the advantages of shared network backup in the light of this new technology. Specifically, this new technology disspells the myth that a fileserver based solution is the only way to achieve high performance.
Plenty has been written about the details of the more common backup solutions. Highlighted below are aspects of these existing applications which are germaine to the goals of the invention.
The earliest network backup applications put the tape device at a workstation, providing a backup solution for files which could be accessed over the network as well as local data. The performance of these applications were limited by local disk performance and network communication overhead. The result is software which, however functional, falls quite short of the performance capabilities of the streaming tape devices being introduced into the market. For some time, these particular applications were the only way of doing full server disk backups, which greatly intensified the performance problem.
Today, "shared" backup systems which put the tape device at the file server have become popular. Some of these can back server data up at the theoretical rate of the streaming tape device. They can also be used to back up other servers as well as work stations on the net. However, all data not residing at the "host" server is still backed up quite slowly while continuing to significantly impact the network.
The problem remains, then, that unless a tape device is positioned at nearly every node, overall performance is low and the impact to the network is high. The result is that, for a grouping number of functioning LANs, this essential data management function continues to interrupt normal network operations for prohibitively long periods. These applications purport to add value to streaming tape devices. But, because they have not beerable to fully utilize device potential, they have actually been value reducing.