Abstract: An apparatus and a method to eliminate deadlock in a bi-directionally mirrored data storage system are presented. In some embodiments, a first and a second storage servers have established a mirroring relationship. To prevent deadlock between the storage servers and to reduce write latency, the second storage server may hold data received from the first storage server in a replication queue and send an early confirmation to the first storage server before writing the data to a destination volume if the first storage server is held up due to a lack of confirmation. In another embodiment, when the first storage server writes metadata of a persistent point-in-time image (PPI) to the second storage server, the second storage server may send a confirmation to the first storage server after copying the metadata, but before exporting the PPI at the second storage server.

Abstract: This invention provides a system and method for managing backup and restore operations on a storage system, typically between source storage system and destination storage system using a backup management client that employs a version of the Network Data Management Protocol to interface with the destination file server and generate an “index” of data structures (such as directories and files) from directly from scanning the trees of PCPIs stored on the destination. The management client includes a command line interface for entry of instructions by a user or application and a web-based user interface and allows the index to be displayed as a series of web pages on a graphical user interface. The index can be browsed and selected data structures can be restored to a source filer/file server as desired. All back-ups/PCPIs can be contemporaneously browsed, allowing greater flexibility in selecting a best backup image to restore.

Abstract: A method for backing up a computer file system is disclosed. A first snapshot of the file system is generated at a first time, the first snapshot having first pointers to data blocks of the file system at the first time. A network adapter receives storage operations to write new data to the file system. A second snapshot of the file system is generated at a second time, the second snapshot having second pointers to data blocks of the file system at the second time, the data blocks at the second time including the new data. The first pointers to the second pointers are compared. In response to the second pointers differing from the first pointers, data of the file system which have been changed between the first snapshot and the second snapshot are copied to a backup copy of the file system.

Abstract: A method for transferring data from a source computer to a destination computer, and restarting the source computer transmission after a halt of the transmission, has the following steps. The source computer inserts a checkpoint number into a data stream, the data flowing in the data stream. The checkpoint number is stored at the source computer. The data stream is halted in response to an error in a path of the data stream. The destination computer locates the last checkpoint number successfully received before halting the data stream. The last checkpoint number successfully received before halting the data stream is transferred to the source computer; and the source computer compares it with checkpoint numbers stored in the source computer to determine where in the data stream to resume transfer of the data. Transfer of the data is resumed in response to the last checkpoint number.

Abstract: A system and method for remote asynchronous replication or mirroring of changes in a source file system snapshot in a destination replica file system using a scan (via a scanner) of the blocks that make up two versions of a snapshot of the source file system, which identifies changed blocks in the respective snapshot files based upon differences in volume block numbers identified in a scan of the logical file block index of each snapshot. Trees of blocks associated with the files are traversed, bypassing unchanged pointers between versions and walking down to identify the changes in the hierarchy of the tree. These changes are transmitted to the destination mirror or replicated snapshot. This technique allows regular files, directories, inodes and any other hierarchical structure to be efficiently scanned to determine differences between versions thereof.

Abstract: A system and method for updating a replicated destination file system snapshot with changes in a source file system snapshot, provides an extensible, file system-independent format to transmit a data stream of change data over the network. The format enabled backward compatibility between different versions of applications running on the source and destination through use of discrete header types which, if not recognized by a version of the application are ignored. In addition, the headers, which can carry data, or act as basic headers for follow on data, include expansion space for additional information.

Abstract: A system and method for updating a replicated destination file system snapshot with changes in a source file system snapshot, facilitates construction of a new directory tree on the destination from source update information using a temporary or “purgatory” directory that allows any modified and deleted files on the destination active file system to be associated with (e.g. moved to) the purgatory directory if and until they are reused. In addition, an inode map is established on the destination that maps source inode numbers to destination inode numbers so as to facilitate building of the destination tree using inode/generation number tuples. The inode map allows resynchronization of the source file system to the destination. The inode map also allows association of two or more destination snapshots to each other based upon their respective maps with the source.

Abstract: A system and method for updating a replicated destination file system snapshot with changes in a source file system snapshot, facilitates construction of a new directory tree on the destination from source update information using a temporary or “purgatory” directory that allows any modified and deleted files on the destination active file system to be associated with (e.g. moved to) the purgatory directory if and until they are reused. In addition, an inode map is established on the destination that maps source inode numbers to destination inode numbers so as to facilitate building of the destination tree using inode/generation number tuples. The inode map allows resynchronization of the source file system to the destination. The inode map also allows association of two or more destination snapshots to each other based upon their respective maps with the source.

Abstract: A system and method for inserting checkpoints into a data stream and for restarting an asynchronous transmission of a data stream from a source file system to a destination file system is provided. The data stream can be a set of changes between a base snapshot and incremental snapshot of the source file system for update of a replicated file system on the destination. State information relating to the progress of the source in processing and transmitting the data stream is stored at regular intervals, and a checkpoint number associated with each stored segment of the state information is inserted into the data stream. The destination tracks the fall commitment of each segment of the data stream to persistent storage on the replicated file system. If an error or communication loss requires the data transfer to be restarted, the destination sends the checkpoint number associated with the last fully committed segment of the data stream.

Abstract: A system and method for updating a replicated destination file system snapshot with changes in a source file system snapshot, provides an extensible, file system-independent format to transmit a data stream of change data over the network. The format enabled backward compatibility between different versions of applications running on the source and destination through use of discrete header types which, if not recognized by a version of the application are ignored. In addition, the headers, which can carry data, or act as basic headers for follow on data, include expansion space for additional information.

Abstract: A system and method for remote asynchronous replication or mirroring of changes in a source file system snapshot in a destination replica file system using a scan (via a scanner) of the blocks that make up two versions of a snapshot of the source file system, which identifies changed blocks in the respective snapshot files based upon differences in volume block numbers identified in a scan of the logical file block index of each snapshot. Trees of blocks associated with the files are traversed, bypassing unchanged pointers between versions and walking down to identify the changes in the hierarchy of the tree. These changes are transmitted to the destination mirror or replicated snapshot. This technique allows regular files, directories, inodes and any other hierarchical structure to be efficiently scanned to determine differences between versions thereof.

Abstract: A system and method for updating a replicated destination file system snapshot with changes in a source file system snapshot, facilitates construction of a new directory tree on the destination from source update information using a temporary or “purgatory” directory that allows any modified and deleted files on the destination active file system to be associated with (e.g. moved to) the purgatory directory if and until they are reused. In addition, an inode map is established on the destination that maps source inode numbers to destination inode numbers so as to facilitate building of the destination tree using inode/generation number tuples. The inode map allows resynchronization of the source file system to the destination. The inode map also allows association of two or more destination snapshots to each other based upon their respective maps with the source.

Abstract: A system and method for updating a replicated destination file system snapshot with changes in a source file system snapshot, facilitates construction of a new directory tree on the destination from source update information using a temporary or “purgatory” directory that allows any modified and deleted files on the destination active file system to be associated with (e.g. moved to) the purgatory directory if and until they are reused. In addition, an inode map is established on the destination that maps source inode numbers to destination inode numbers so as to facilitate building of the destination tree using inode/generation number tuples. The inode map allows resynchronization of the source file system to the destination. The inode map also allows association of two or more destination snapshots to each other based upon their respective maps with the source.

Abstract: A system and method for updating a replicated destination file system snapshot with changes in a source file system snapshot, provides an extensible, file system-independent format to transmit a data stream of change data over the network. The format enabled backward compatibility between different versions of applications running on the source and destination through use of discrete header types which, if not recognized by a version of the application are ignored. In addition, the headers, which can carry data, or act as basic headers for follow on data, include expansion space for additional information.

Abstract: A system and method for remote asynchronous replication or mirroring of changes in a source file system snapshot in a destination replica file system using a scan (via a scanner) of the blocks that make up two versions of a snapshot of the source file system, which identifies changed blocks in the respective snapshot files based upon differences in volume block numbers identified in a scan of the logical file block index of each snapshot. Trees of blocks associated with the files are traversed, bypassing unchanged pointers between versions and walking down to identify the changes in the hierarchy of the tree. These changes are transmitted to the destination mirror or replicated snapshot. This technique allows regular files, directories, inodes and any other hierarchical structure to be efficiently scanned to determine differences between versions thereof.