Systems and methods for backing up data files

Details Systems and methods for backing up data files Systems and methods for backing up data files

1999-12-16

2003-02-25

Alam, Shahid (Department: 2172)

Data processing: database and file management or data structures

Database design

Data structure types

C707S793000, C707S793000, C707S793000, C709S236000, C711S162000, C713S176000, C714S004110, C714S005110

Reexamination Certificate

active

06526418

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to systems and methods for maintaining back up files for servers on a computer network, and more specifically, to systems and method for continuously backing up data files stored on a computer network.
BACKGROUND OF THE INVENTION
Computer networks have been remarkably successful at processing, communicating and storing of vast amounts of data. As companies today become more accustomed to storing important company information on their data network, the value of these networks and the data they store continues to grow. IN fact, many companies now identify the data stored on their computer network as their most valuable corporate asset. Accordingly, it is an important function of a network administrator to, from time to time, backup to a long term storage medium, the data on the corporate network.
Today most backup systems operate by having the network administrator identify a time of day during which little or no network activity occurs. During this time the network administrator turns the network over to a backup system and the data files stored on the computer network are backed up, file by file, to a long term storage medium, such as a tape backup system. Typically the network administrator will backup once a week, or even once a day, to ensure that the back up files are current.
Although such a backup process may work well to create a copy of the data stored on the network, it is a time consuming and labor intensive process. Moreover, it is a cumbersome process that often is inappropriate in many environments. For example, as more and more computer networks begin to operate twenty-four hours a day seven days week, it is continuously more difficult for the system administrator to identify a block of time during which the majority of network resources may be turned over to the backup procedure. Moreover, as computerized network systems begin to store more information as well as information that changes regularly during the course of the work day, the value of a backup system which only backups once a week or once a day is fairly reduced. In fact many companies now rely on the corporate network to store almost all of its business information, and the loss of even a portion of the information stored on the network during the course of a day may result in a substantial cost for the company. Accordingly, systems which only backup periodically are of a reduced value to a company.
Moreover, although the current backup systems work well for putting data on to a long term storage media system, they often store data sequentially on to media, like a magnetic tape, losing the file structure of the data, and making it difficult to retrieve information without having to reinstall all the data previously stored on the tape. Thus, if a portion of the data is lost, it is often difficult to restore just the data that was lost, and often the system administrator is forced to decide whether it is worth the cost of retrieving the lost portion of the data.
Accordingly, there is a need in the art for backup systems that are less obtrusive, may continuously update the data stored on a network, and make it more facile for a system administrator to retrieve data, or portions of data, stored to a computer network.
SUMMARY OF THE INVENTION
The systems and methods described herein provide for continuous back up of data stored on a computer network. To this end the systems of the invention include a synchronization replication process that replicates selected source data files data stored on the network to create a corresponding set of replicated data files, called the target data files, that are stored on a back up server. This synchronization replication process builds a baseline data structure of target data files. In parallel to this synchronization process, the system includes a dynamic replication process that includes a plurality of agents, each of which monitors file access operations for a server on the network to detect and capture, at the byte-level, changes to the source data files. Each agent may record the changes to a respective journal file, and as the dynamic replication process detects that the journal files contain data, the journal files are transferred or copied to the back up server so that the captured changes can be written to the appropriate ones of the target data files.
More particularly, in one aspect the invention provides a system for creating backup files for data files stored on a computer network. Such a system comprises a backup server that has storage for a plurality of data files, a data server having a source data file and an agent operating on the data server and capable of capturing changes to the source data file as the source data file is being modified and capable of recording detected changes within a journal file. The system can further comprise a synchronization replication process for replicating the source data file to create a target data file stored on the backup server, and a dynamic replication process that is responsive to data within the journal file for altering the target data file to mirror changes made to the source data file.
In one embodiment the agent may comprise a process such as a computer process that is capable of monitoring a file access operation that occurs on the data server for determining whether the source data file is open. To this end, the agent may comprise a file system filter (FSF) process that can detect file input and output calls to or through the operating system. Therefore the agent may monitor file access operations to record byte level modifications to the source data file, and these byte level modifications may be recorded within the journal file as modifications made to the source data file. The agent may also include a time stamp mechanism for providing a time stamp to the journal file thereby indicating the time of recording the modifications to the source data file. Additionally, this file system filter can be utilized to allow the agent process to have unrestricted access to all files on the source system, regardless of how the applications have tried to restrict access. This means even if the applications open the file in a share restricted manner, the file system filter will allow the agent process access to this file.
The synchronization replication process may include an image capture mechanism that can process a file system or data structure on the server and create a file system image signal that is representative of the state, or a state, of the file system at a particular time. For example, the image capture mechanism can include a directory processor that can process a directory structure such as a conventional UNIX file system or windows NT file system directory structure, to create a directory image signal which is representative of a state of the directory at the time of processing that directory structure. In one embodiment the image generator operates by processing metadata associated with a data structure of file structure such as the size of the data structure, the size of directory, the name to the files and directory, the metadata associated with the last time the directory was edited, or when it was created, the n umber of files in the directory, and other such metadata. A hashing process of cyclical redundancy check (CRC) process may be applied to the metadata to come up with an identifier that is uniquely, or substantially uniquely, representative of the state of the processed file structure at the time of the processing. A similar image generator process may be employed for processing a file system on the server to create a file system image signal that is representative of a state of a file, directory, or the data within a file. In either case, the image signal is representative of a state of the file structure, such as the directory, a group of files in a directory, a particular file, or even a particular portion of a file.
In one embodiment the dynamic replication process may include a process for monitoring a journal file and in response to detec

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