Abstract: A method and system for mirroring and archiving mass storage. A primary mass storage and a secondary mass storage are synchronized to contain the same data. Thereafter, a primary system tracks changes made to the primary mass storage. These changes are consolidated periodically into update files, the consolidations representing changes made to the primary mass storage during a time interval that ends when the primary mass storage is in a logically consistent state. These update files contain only those changes necessary to represent the modified state of the primary mass storage at the time of the update. The primary system then transfers the update files to a secondary system to bring the secondary mass storage current with the primary mass storage. The consolidation minimizes the amount of information that must be transferred and therefore allows for a relatively low band width communication channel.

Abstract: Data blocks lost at a primary mass storage are restored while allowing the primary computer system to access the lost data block before full restoration. Restoration occurs along two channels. In the first channel, read requests issued by the primary computer system are handled by obtaining the requested data block from the backup mass storage device. The retrieved data block is then written to the primary mass storage, thereby restoring the primary mass storage for that data block. In the second channel of restoration, a snapshot copy of a selected data set of the backup mass storage is made and transported to the primary system. If the corresponding data block in the primary mass storage has a current data block, the data block is not written from the snapshot copy to the primary mass storage. Otherwise, the data block is copied from the snapshot copy to the primary mass storage.

Abstract: Maintaining logically consistent backups using minimal data transfer. A backup, or snapshot, copy of original data is created and stored. A user designates data blocks that are to be backed up in a process of creating a subsequent snapshot copy of the data. Data blocks that are to be backed up might include those associated with active files having data of interest to the user. Data blocks that are not desired for backup might include, for example, swap files, printer buffers and temp files. The changes that have been made to the data blocks that have been designated for backup are applied to the snapshot copy after a specified time period has elapsed. Since only desired data blocks are backed up to the snapshot copy, memory, processing cycles and communication bandwidth are used more efficiently than if all data blocks were to be backed up to the snapshot copy.

Abstract: Maintaining logically consistent backups using minimal data transfer. A backup, or snapshot, copy of original data is created and stored. A user designates data blocks that are to be backed up in a process of creating a subsequent snapshot copy of the data. Data blocks that are to be backed up might include those associated with active files having data of interest to the user. Data blocks that are not desired for backup might include, for example, swap files, printer buffers and temp files. The changes that have been made to the data blocks that have been designated for backup are applied to the snapshot copy after a specified time period has elapsed. Since only desired data blocks are backed up to the snapshot copy, memory, processing cycles and communication bandwidth are used more efficiently than if all data blocks were to be backed up to the snapshot copy.

Abstract: A method and system for mirroring and archiving mass storage. A primary mass storage and a secondary mass storage are synchronized to contain the same data. Thereafter, a primary system tracks changes made to the primary mass storage. These changes are consolidated periodically into update files, the consolidations representing changes made to the primary mass storage during a time interval that ends when the primary mass storage is in a logically consistent state. These update files contain only those changes necessary to represent the modified state of the primary mass storage at the time of the update. The primary system then transfers the update files to a secondary system to bring the secondary mass storage current with the primary mass storage. The consolidation minimizes the amount of information that must be transferred and therefore allows for a relatively low band width communication channel.

Abstract: Data blocks lost at a primary mass storage are restored while allowing the primary computer system to access the lost data block before full restoration. Restoration occurs along two channels. In the first channel, read requests issued by the primary computer system are handled by obtaining the requested data block from the backup mass storage device. The retrieved data block is then written to the primary mass storage, thereby restoring the primary mass storage for that data block. In the second channel of restoration, a snapshot copy of a selected data set of the backup mass storage is made and transported to the primary system. If the corresponding data block in the primary mass storage has a current data block, the data block is not written from the snapshot copy to the primary mass storage. Otherwise, the data block is copied from the snapshot copy to the primary mass storage.

Abstract: Restoring a mass storage device, including the corresponding data blocks stored thereon, to a state in which it existed at a prior instant in time to minimize the data loss caused by data blocks becoming corrupt or lost. After a mirrored or backup copy has been made, data blocks that are to be overwritten in response to a write request are stored in a preservation memory prior to being overwritten. The data blocks stored in the preservation memory are time-stamped to designate the chronological order by which the data blocks were overwritten. If data becomes corrupted, the data blocks of the preservation memory are applied to the corrupted data in reverse chronological order until such time that a valid, non-corrupted set of data is obtained. In this manner, data more recent than that associated with the full mirrored or backup copy can be reconstructed.

Abstract: A method and system for mirroring and archiving mass storage. A primary mass storage and a secondary mass storage are synchronized to contain the same data. Thereafter, a primary system tracks changes made to the primary mass storage. These changes are consolidated periodically into update files, the consolidations representing changes made to the primary mass storage during a time interval that ends when the primary mass storage is in a logically consistent state. These update files contain only those changes necessary to represent the modified state of the primary mass storage at the time of the update. The primary system then transfers the update files to a secondary system to bring the secondary mass storage current with the primary mass storage. The consolidation minimizes the amount of information that must be transferred and therefore allows for a relatively low band width communication channel.

Abstract: A method and system for mirroring and archiving mass storage. A primary mass storage and a secondary mass storage are synchronized to contain the same data. Thereafter, a primary system tracks changes made to the primary mass storage. These changes are consolidated periodically into update files, the consolidations representing changes made to the primary mass storage during a time interval that ends when the primary mass storage is in a logically consistent state. These update files contain only those changes necessary to represent the modified state of the primary mass storage at the time of the update. The primary system then transfers the update files to a secondary system to bring the secondary mass storage current with the primary mass storage. The consolidation minimizes the amount of information that must be transferred and therefore allows for a relatively low band width communication channel.

Abstract: Maintaining logically consistent backups using minimal data transfer. A backup, or snapshot, copy of original data is created and stored. A user designates data blocks that are to be backed up in a process of creating a subsequent snapshot copy of the data. Data blocks that are to be backed up might include those associated with active files having data of interest to the user. Data blocks that are not desired for backup might include, for example, swap files, printer buffers and temp files. The changes that have been made to the data blocks that have been designated for backup are applied to the snapshot copy after a specified time period has elapsed. Since only desired data blocks are backed up to the snapshot copy, memory, processing cycles and communication bandwidth are used more efficiently than if all data blocks were to be backed up to the snapshot copy.

Abstract: A method for providing rapid recovery from a network file server failure through the use of a backup computer system. The backup computer system runs a special mass storage access program that communicates with a mass storage emulator program on the network file server, making the disks or other mass storage devices on the backup computer system appear like they were disks on the file server computer. By mirroring data by writing to both the mass storage of the file server and through the mass storage emulator and mass storage access program to the disks on the backup computer, a copy of the data on the file server computer is made. Optionally, selected portions of the data read through the mass storage emulator program can be altered before being returned as the result of the read operation on the file server. In the event of failure of the file server computer, the backup computer can replace the file server, using the copy of the file server's data stored on its disks.

Abstract: A method and system for mirroring and archiving mass storage. A primary mass storage and a secondary mass storage are synchronized to contain the same data. Thereafter, a primary system tracks changes made to the primary mass storage. These changes are consolidated periodically into update files, the consolidations representing changes made to the primary mass storage during a time interval that ends when the primary mass storage is in a logically consistent state. These update files contain only those changes necessary to represent the modified state of the primary mass storage at the time of the update. The primary system then transfers the update files to a secondary system to bring the secondary mass storage current with the primary mass storage. The consolidation minimizes the amount of information that must be transferred and therefore allows for a relatively low band width communication channel.

Abstract: Restoring a mass storage device, including the corresponding data blocks stored thereon, to a state in which it existed at a prior instant in time to minimize the data loss caused by data blocks becoming corrupt or lost. After a mirrored or backup copy has been made, data blocks that are to be overwritten in response to a write request are stored in a preservation memory prior to being overwritten. The data blocks stored in the preservation memory are time-stamped to designate the chronological order by which the data blocks were overwritten. If data becomes corrupted, the data blocks of the preservation memory are applied to the corrupted data in reverse chronological order until such time that a valid, non-corrupted set of data is obtained. In this manner, data more recent than that associated with the full mirrored or backup copy can be reconstructed.

Abstract: Data blocks lost at a primary mass storage are restored while allowing the primary computer system to access the lost data block before full restoration. Restoration occurs along two channels. In the first channel, read requests issued by the primary computer system are handled by obtaining the requested data block from the backup mass storage device. The retrieved data block is then written to the primary mass storage, thereby restoring the primary mass storage for that data block. In the second channel of restoration, a snapshot copy of a selected data set of the backup mass storage is made and transported to the primary system. If the corresponding data block in the primary mass storage has a current data block, the data block is not written from the snapshot copy to the primary mass storage. Otherwise, the data block is copied from the snapshot copy to the primary mass storage.

Abstract: A method and system for mirroring and archiving mass storage. A primary mass storage and a secondary mass storage are synchronized to contain the same data. Thereafter, a primary system tracks changes made to the primary mass storage. These changes are consolidated periodically into update files, the consolidations representing changes made to the primary mass storage during a time interval that ends when the primary mass storage is in a logically consistent state. These update files contain only those changes necessary to represent the modified state of the primary mass storage at the time of the update. The primary system then transfers the update files to a secondary system to bring the secondary mass storage current with the primary mass storage. The consolidation minimizes the amount of information that must be transferred and therefore allows for a relatively low band width communication channel.

Abstract: A method and system for mirroring and archiving mass storage. A primary mass storage and a secondary mass storage are synchronized to contain the same data. Thereafter, a primary system tracks changes made to the primary mass storage. These changes are consolidated periodically into update files, the consolidations representing changes made to the primary mass storage during a time interval that ends when the primary mass storage is in a logically consistent state. These update files contain only those changes necessary to represent the modified state of the primary mass storage at the time of the update. The primary system then transfers the update files to a secondary system to bring the secondary mass storage current with the primary mass storage. The consolidation minimizes the amount of information that must be transferred and therefore allows for a relatively low band width communication channel.

Abstract: A method for providing rapid recovery from a network file server failure through the use of a backup computer system. The backup computer system runs a special mass storage access program that communicates with a mass storage emulator program on the network file server, making the disks (or other mass storage devices) on the backup computer system appear like they were disks on the file server computer. By mirroring data by writing to both the mass storage of the file server and through the mass storage emulator and mass storage access program to the disks on the backup computer, a copy of the data on the file server computer is made. Optionally, selected portions of the data read through the mass storage emulator program can be altered before being returned as the result of the read operation on the file server. In the event of failure of the file server computer, the backup computer can replace the file server, using the copy of the file server's data stored on its disks.

Abstract: A method for providing rapid recovery from a network file server failure through the use of a backup computer system. The backup computer system runs a special mass storage access program that communicates with a mass storage emulator program on the network file server, making the disks (or other mass storage devices) on the backup computer system appear like they were disks on the file server computer. By mirroring data by writing to both the mass storage of the file server and through the mass storage emulator and mass storage access program to the disks on the backup computer, a copy of the data on the file server computer is made. Optionally, selected portions of the data read through the mass storage emulator program can be altered before being returned as the result of the read operation on the file server. In the event of failure of the file server computer, the backup computer can replace the file server, using the copy of the file server's data stored on its disks.

Abstract: A system and method for providing a static snapshot, or image, of data stored on a mass storage system are disclosed. First, a preservation memory is cleared and a virtual device is created. Whenever a write is to be performed on the mass storage system, a check is made of the preservation memory to determine if it contains a block associated with the mass storage write address. If there is not, a copy of the block in the mass storage system at the block write address is placed in the preservation memory. Whenever a read is to be performed on the virtual device, a check is made of the preservation memory to determine if it contains a block associated with the virtual device read address. If there is such a block, that block is returned as the result of the virtual device read. Otherwise, the block at the virtual device block read address is returned as the result.