Abstract:
Techniques for creating checkpoints are disclosed. In one particular exemplary embodiment, the techniques may be realized as a method for creating file system checkpoints comprising the steps of modifying a first data block and a second data block with a first transaction, associating the first data block with a first stamp, and associating the second data block with a second stamp, wherein the first stamp and the second stamp are substantially similar.

Description:
FIELD OF THE DISCLOSURE 
     The present disclosure relates generally to continuous data protection and, more particularly, to techniques for creating checkpoints. 
     BACKGROUND OF THE DISCLOSURE 
     A continuous data protection (“CDP”) system associated with a target system may capture changes to memory blocks associated with one or more changes in a file system or memory of the target system. The target system may, for example, be a server or other computerized system in which it may be advantageous to have the ability to create one or more snapshots of the current state of the file system or memory. The target system may operate one or more applications, which may be operable to create changes to the memory. The changes to the memory may be handled by a memory cache, which then may create one or more changes to the file system. 
     The target system may be operable to transmit each changed memory block to the CDP system. Either the target system or the CDP system may associate each changed block with a time stamp denoting the current time. The CDP may store the changed blocks and the associated time stamps in a file system or memory such as, for example, in one or more files on a hard disk drive or in a database. Should the file system or memory need to be restored, a time for restoration may be used. For example, the file system or memory may be recreated as it existed at a time T 1 . The CDP may be operable to recreate the file system or memory at time T 1  using all of the blocks that the CDP received on or before time T 1 . 
     Problems with the above-described CDP systems may arise because one or more discrete blocks may not always encompass an entire change or transaction to the file system or memory. In other words, the memory changes created by one or more of the applications on the target system may not be fully embodied in the CDP system at time t 1 . A restore at time T 1  may create a file system or memory that is internally inconsistent, and may also creating inconsistencies at the application level. For example, a block containing a part of file x.dat may have been transmitted to the CDP before time T 1 , but another block containing another part of file x.dat may have been transmitted to the CDP after time T 1 . Therefore, a restore of the file system or memory to time T 1  may yield a partial change to file x.dat, possibly resulting in a file corruption issue. Or, the file x.dat may have been fully transmitted to the CDP, but metadata describing file x.dat may not have been transmitted to the CDP system, or vice versa. So the metadata describing the file may be inconsistent with the file itself if a restore is required between a time the file was transferred to the CDP system and a time the metadata was transferred to the CDP system. This problem may be replicated across many different files. The file system or memory thus must be placed into a consistent state before it may be fully restored for use. This operation of placing a file system or memory in a consistent state may be very expensive in terms of time and processor or memory resources. 
     In view of the foregoing, it may be understood that there are significant problems and shortcomings associated with current continuous data protection technologies. 
     SUMMARY OF THE DISCLOSURE 
     Techniques for creating checkpoints are disclosed. In one particular exemplary embodiment, the techniques may be realized as a method for creating file system checkpoints comprising the steps of modifying a first data block and a second data block with a first transaction, associating the first data block with a first stamp, and associating the second data block with a second stamp, wherein the first stamp and the second stamp are substantially similar. 
     In accordance with other aspects of this particular exemplary embodiment, the method further comprises transmitting the first data block and the first stamp to a continuous data protection system. 
     In accordance with further aspects of this particular exemplary embodiment, the method further comprises transmitting the second data block and the second stamp to a continuous data protection system. 
     In accordance with additional aspects of this particular exemplary embodiment, a third data block is associated with a third stamp, where the third stamp is dissimilar to the first stamp and the second stamp and where the third block is modified by a second transaction. 
     In accordance with further aspects of this particular exemplary embodiment, the method further comprises creating a shadow block of the second data block and associating the shadow block with a third stamp, where the third stamp is dissimilar to the first stamp and the second stamp and where the shadow block is modified by a second transaction. 
     In accordance with additional aspects of this particular exemplary embodiment, the method further comprises associating a first time stamp with the first data block, and associating a second time stamp with the second data block. 
     In accordance with further aspects of this particular exemplary embodiment, at least one signal embodied in at least one carrier wave for transmitting a computer program of instructions configured to be readable by at least one processor for instructing the at least one processor to execute a computer process for performing the method as recited is provided. 
     In accordance with additional aspects of this particular exemplary embodiment, at least one processor readable carrier for storing a computer program of instructions configured to be readable by at least one processor for instructing the at least one processor to execute a computer process for performing the method is provided. 
     In another particular exemplary embodiment, the techniques may be realized as a system for creating file system checkpoints comprising an I/O module operable to transmit one or more data blocks, a CDP module operable to transmit one or more data blocks to one or more CDP systems, a stamp module operable to associate a stamp to the one or more data blocks before transmission by the CDP module. 
     In accordance with other aspects of this particular exemplary embodiment, the I/O module, the CDP module, and the stamp module are in communication with each other. 
     In accordance with further aspects of this particular exemplary embodiment, the CDP module is in communication with a CDP system. 
     In another particular exemplary embodiment, the techniques may be realized as a system for system for creating file system checkpoints comprising means for associating a first data block with a first stamp, and means for associating a second data block with a second stamp, where the first stamp and the second stamp are substantially similar and where the first data block and the second data block are modified by a first transaction. 
     In accordance with other aspects of this particular exemplary embodiment, the system further comprises means for transmitting the first data block and the first stamp to a continuous data protection system. 
     In accordance with further aspects of this particular exemplary embodiment, the system further comprises means for transmitting the second data block and the second stamp to a continuous data protection system. 
     In accordance with additional aspects of this particular exemplary embodiment, a third data block is associated with a third stamp, where the third stamp is dissimilar to the first stamp and the second stamp and where the third block is modified by a second transaction. 
     In accordance with additional aspects of this particular exemplary embodiment, the system further comprises creating a shadow block of the second data block and associating the shadow block with a third stamp, where the third stamp is dissimilar to the first stamp and the second stamp and where the shadow block is modified by a second transaction. 
     In accordance with additional aspects of this particular exemplary embodiment, the system further comprises means for associating a first time stamp with the first data block, and means for associating a second time stamp with the second data block. 
     The present disclosure will now be described in more detail with reference to exemplary embodiments thereof as shown in the accompanying drawings. While the present disclosure is described below with reference to exemplary embodiments, it should be understood that the present disclosure is not limited thereto. Those of ordinary skill in the art having access to the teachings herein will recognize additional implementations, modifications, and embodiments, as well as other fields of use, which are within the scope of the present disclosure as described herein, and with respect to which the present disclosure may be of significant utility. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to facilitate a fuller understanding of the present disclosure, reference is now made to the accompanying drawings, in which like elements are referenced with like numerals. These drawings should not be construed as limiting the present disclosure, but are intended to be exemplary only. 
         FIG. 1  shows a diagram view of a system including a continuous data protection system in accordance with an embodiment of the present disclosure; 
         FIG. 2  shows the flow of data from a system to a continuous data protection system in accordance with an embodiment of the present disclosure; 
         FIG. 3  shows a diagram of a system transmitting blocks to a CDP system in accordance with an embodiment of the present disclosure; 
         FIG. 4  shows a diagram of a system transmitting blocks to a CDP system in accordance with another embodiment of the present disclosure; and 
         FIG. 5  shows a flow chart of a method for transmitting blocks to a CDP system in accordance with an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     The description below is intended to be exemplary of the techniques for creating checkpoints embodied in the present disclosure. An example of a file system is used for illustrative purposes, but the present disclosure may be used according to other embodiments to create a application consistent or application level checkpoints. 
     Referring to  FIG. 1 , a diagram level overview of a system  100  is shown in accordance with an embodiment of the present disclosure. The system  100  may comprise a system interface module  101 , a stamp module  103 , a CDP interface module  105 , and an input/output (“I/O”) module  107 . Each module may interact with each other module. In one embodiment, the modules may be contained within one physical system, but this is not necessary. In another embodiment, one or more modules may be placed on one or more physical systems, for example on one or more computers. The one or more computers, and the one or more modules which may reside on the one or more computers, may be in communication via a network. The system  100  may contain one or more modules, such as the system interface module  101 , the stamp module  103 , the CDP interface module  105 , or the I/O module  107 . Each module will be explained in more detail below. 
     The system interface module  101  may be operable to permit or allow some or all of the other modules to interact with one another. The interaction may allow one or more of the modules to transmit signals to another one or more of the modules, or the system interface module  101  may selectively permit signals to be transmitted between one or more modules. The signals may constitute packets of data, or other types of signals transmitted between one or more modules and one or more other modules. 
     The stamp module  103  may be operable to associate one or more stamps with one or more data blocks. The data blocks may be located on the same system  100  as the stamp module  103 , or may be located on another system in communication with the stamp module  103 . For example, the stamp module  103  may associate stamps with one or more stores of random access memory (“RAM”) on the system  100 . Or, the stamp module  103  may associate stamps with one or more electronic files on a storage area network, or another networked file system, or may utilize one or more networks, including, without limitation, the internet, to read one or more electronic files from a remote system. 
     The CDP interface module  105  may be in communication with a continuous data protection system  130  (“CDP system”). The CDP interface module  105  may be operable to send one or more data blocks, or one or more data blocks with an associated stamp, to the CDP system  130 . 
     The CDP system  130  may be another system, separate from the system  100 , or may be located within the same physical space. If the CDP system  130  and the system  100  are located separately from one another, then the CDP system  130  and the system  100  may be in communication with one another. The method of communication may take any form of communicating data between systems. For example, the system  100  and the CDP system  130  may communicate via a wire or a wireless link, or may be connected via a network. The CDP system  130  may contain one or more CDP stores, operable to store the data blocks communicated via the CDP interface module  105 . The one or more CDP stores may be one or more electronic files, or may be contained within one or more databases. The CDP system  130  may be operable to recall one or more of the one or more data blocks communicated via the CDP interface module  105  and stored in one or more of the one or more CDP stores. 
     The I/O module  107  may be operable to read input from one or more input devices and write output to one or more output devices. The I/O module  107  may be in communication with memory or storage devices  210  associated with the system  100 , and may be in communication with the CDP interface module  105 , so that data blocks modified by the system  100  may be communicated to the memory or storage devices  210  associated with the system  100  and also with the CDP interface module  105 . 
     Turning now to  FIG. 2 , a flow of data from the system  100  to the CDP system  130  is shown in accordance with an embodiment of the present disclosure. The system  100 , and the memory and storage devices  210  associated with the system  100 , may be in communication. The memory and storage devices  210  associated with the system  100  may include, but are not limited to, RAM, a magnetic hard drive, optical storage, or a tape drive. The system  100  may read information from the memory and storage devices  210 , and may write information to the memory and storage devices  210 . Reading and writing information may occur by requesting one or more blocks from the memory and storage devices  210 , and writing one or more blocks to the memory and storage devices  210 . When the system  100  sends an updated memory block to the memory and storage devices  210 , the stamp module  103 , either working with the I/O module  107  and/or the CDP interface module  105  or separate from the I/O module  107  and CDP interface module  105 , may associate the updated memory block with a stamp. The updated memory block and the associated stamp may then be transmitted to the CDP system  130  via the CDP interface module  105 . Therefore, the updated memory block may be transmitted to the memory and storage devices  210 , but the updated memory block may also be associated with a stamp and transmitted, and may be stored in the CDP system  130 . 
     Turning now to  FIG. 3 , a diagram of the system  100  transmitting blocks to the CDP system  130  is shown in accordance with an embodiment of the present disclosure. Blocks in the diagram may be transmitted sequentially from the top of the diagram to the bottom of the diagram. For example, the system  100  may create and transmit Block 1   401  at a time Time 1 , Block 2   403  at a time Time 2 , Block 3   405  at a time Time 3 , Block 4   407  at a time Time 4 , and Block 5   409  at a time Time 5 . However, Block 1   401  and Block 2   403  may contain pieces of the same logical file for example, or Block 1   401  may contain a logical file and Block 2   403  may contain metadata describing the file contained in Block 1   401  that are a part of the same transaction. 
     In the embodiment of the present disclosure, the stamp module  103  may be operable to associate a time stamp with one or more data blocks which may or may not be the current time. For example, the stamp module  103  may associate a stamp T 1  with Block 1   401 , and the system  100  may transmit Block 1   401  associated with stamp T 1  to the CDP system  130 . The stamp module  103  may also associate a stamp T 1  with Block 2   403 , and the system  100  may transmit Block 2   403  associated with stamp T 1  to the CDP system  130 , even though Block 2   403  was transmitted to the CDP system  130  at a time Time 2 . The CDP system  130  may thus store Block 1   401  with a stamp of T 1  and Block 2   403  with a stamp of T 1 . 
     A similar procedure may be followed even if associated blocks are not consecutively transferred to the CDP system  130 . For example, in  FIG. 3 , Block 3   405  and Block 5   409  may contain information about a single file, similar to Block 1   401  and Block 2   403 . The system  100  may associate Block 3   405  and Block 5   409  together and may assign a stamp of T 2  to Block 3   405 . If Block 3   405  is transmitted to the CDP system  130 , the system  100  may transmit other blocks to the CDP system  130  between Block 3   405  and Block 5   409 . In this example, Block 4   407 , which may be a memory block unrelated to the file or files contained in Block 3   405  and Block 5   409 , may be transmitted to the CDP system  130  at time Time 4 . Block 4   407  may be associated with a different stamp than Block 3   405  and Block 5   409 , since the file or files in Block 4   407  may be different than in Block 3   405  and Block 5   409 . After Block 4   407  is transmitted to the CDP system  130  at a time Time 4 , Block 5   409 , associated with stamp T 2 , may be transmitted to the CDP system  130  at a time Time 5 . 
     The CDP system  130  may receive data blocks from the system  100  and may store each data block along with the stamp that is associated with it. The CDP system  130  may be operable to transmit one or more data blocks to the system  100 , and may be operable to selectively transmit data blocks to the system  100  based on a selected stamp. For example, if the system  100  requested a restoration image at time Time 1 , the CDP system  130  may transmit Block 1   401  and Block 2   403  to the system  100 , even though Block 2   403  may have been transmitted to the CDP system  130  at a time Time 2 , since the system  100  and the stamp module  103  may have associated it with a stamp T 1 . If the system  100  requested a restoration image at time Time 2 , the CDP system  130  may transmit Block 1   401 , Block 2   403 , Block 3   405 , and Block 5   409  to the system  100 . Block 5   409  may be transmitted to the system  100  from the CDP system  130  because it may be associated with a stamp T 2 , even though it may have been transmitted at a time Time 5 . Block 4   407  may not be transmitted to the system  100 , as it may have been transmitted at a time Time 4 , and may contain a stamp of T 4 . Of course, the system  100  may transmit more or fewer blocks;  FIG. 3  is intended as exemplary of one possible process. 
     Turning now to  FIG. 4 , a diagram of the system  100  transmitting blocks to the CDP system  130  is shown in accordance with another embodiment of the present disclosure. In this embodiment, the system  100  may associate two or more stamps with the data blocks when transmitting them to the CDP system  130 . Blocks in the diagram may be transmitted sequentially from the top of the diagram to the bottom of the diagram. One stamp may be a unique identifier, and may be similar to the stamp described above. Another stamp may be a time stamp written by the system  100  or the CDP system  130 . The time stamp may reflect the current time at the system  100  or the CDP system  130 , or may reflect another time. The time stamp may be unique to each data block, or the time recorded within the time stamp may be long enough for one or more blocks to share the same time stamp. 
     For example, the stamp module  103  may associate a stamp T 1  with Block 1   501 , and the system  100  may transmit Block 1   501  associated with stamp T 1  to the CDP system  130  at a time T 1 . The stamp module  103  may also associate a stamp T 1  with Block 2   503 , and the system  100  may transmit Block 2   503  associated with stamp T 1  to the CDP system  130  at a time T 2 . The CDP system  130  may thus store Block 1   501  with a stamp of T 1  and a time stamp of Time 1 , and Block 2   503  with a stamp of T 1  and a time stamp of Time 2 . 
     A similar procedure may be followed even if associated blocks are not consecutively transferred to the CDP system  130 , similar to  FIG. 3 . For example, in  FIG. 4 , Block 3   505  and Block 5   509  may contain information about a single file, similar to Block 1   501  and Block 2   503 . The system  100  may associate Block 3   505  and Block 5   509  together and may assign a stamp of T 2  to Block 3   505 . If Block 3   505  is transmitted to the CDP system  130  at a time Time 3 , the system  100  may transmit other blocks to the CDP system  130  between Block 3   505  and Block 5   509 . In this example, Block 4   507 , which may be a memory block unrelated to the file or files contained in Block 3   505  and Block 5   509 , may be transmitted to the CDP system  130  at a time Time 4 . Block 4   507  may be associated with a different stamp than Block 3   505  and Block 5   509 , since the file or files in Block 4   507  may be different than in Block 3   505  and Block 5   509 . After Block 4   507  is transmitted to the CDP system  130  at a time Time 4 , Block 5   509 , associated with stamp T 2 , may be transmitted to the CDP system  130  at a time Time 5 . 
     The CDP system  130  shown in  FIG. 4  may operate similarly to the CDP system  130  shown in  FIG. 3 , except that the CDP system  130  shown in  FIG. 4  may be operable to store data blocks and associate two or more stamps with the data blocks. For example, when the system  100  transmits data Block 1   501  with associated stamp T 1  to the CDP system  130  at time Time 1 , the CDP system  130  may be operable to store data Block 1   501  and also store the stamp T 1  and time stamp Time 1  associated with Block 1   501 . When the system  100  transmits data Block 2   503  with associated stamp T 1  to the CDP system  130  at time Time 2 , the CDP system  130  may be operable to store data Block 2   503  and also store the stamp T 1  and time stamp Time 2  associated with Block 2   503 . 
     The CDP system  130  may be operable to transmit one or more of the data blocks to the system  100  based on any of the stamps, or based on a combination of one or more of the two or more stamps. For example, if the system  100  requested all data blocks on before a time Time 2 , the CDP module  105  may be operable to transmit the data blocks that had a time stamp of the time on or before time Time 2 . The CDP system  130  may also be operable to transmit the data blocks that had a time stamp of the time on or before time Time 2 , as well as blocks that had similar stamps to the blocks with a time stamp of the time on or before time Time 2 , even if the data blocks had a time stamp after time Time 2 . In the  FIG. 4  example, if the system  100  requested all blocks on or before time Time 1 , the CDP system  130  may be operable to transmit both Block 1   501  and Block 2   503 , because Block 1   501 , which has a time stamp of time Time 1 , also shares a stamp T 1  with Block 2   503 , even though Block 2   503  has a time stamp of time Time 2 . 
     Referring now to  FIG. 5 , a flow chart of a method for transmitting blocks to the CDP system  130  is shown in accordance with an embodiment of the present disclosure. As shown in block  601 , the system  100  may receive or generate a modified data block. As shown in block  603 , the system  100  may make a determination that the modified data block from block  601  is associated with a data block generated or received previously, or may be associated with a data block generated or received after the data block shown in block  601 . The system  100  may associate two or more blocks if, for example, they contain parts of one or more common files, or if the blocks have been previously associated, or another method may be used to determine if two or more blocks may be associated with one another. 
     If the data block from block  601  is associated with a previous block, then the system  100  may assign the stamp associated with the previous data block to the data block, as shown in step  607 . If the data block from block  601  is not associated with a previous block, then the system  100  may assign a new stamp to the data block, as shown in block  605 . A block may have a stamp associated with a previous data block, or may have a new stamp associated with it. Additionally, other stamps may be associated with the data block from block  601 . For example, a time stamp may be associated with the data block. After one or more stamps have been associated with the data block from block  601 , the block may be transmitted to the CDP system  130 , as shown in block  609 . The data block and the one or more stamps may be transmitted in a single communication to the CDP system  130 , or may be transmitted separately. For example, the data block may be transmitted via a dedicated input/output link between the system  100  and the CDP system  130 , for example over a SCSI link. The one or more stamps may be transmitted separately via a network, for example over an ethernet link between the system  100  and the CDP system  130 . Alternatively, the block and associated stamps may be held in a queue or cache mechanism on the system  100  so that multiple blocks and associated stamps may be transmitted to the CDP system  130  at once. The CDP system  130  may also employ a queue or cache mechanism so that multiple blocks and associated stamps may be stored in the CDP system  130 . For example, a queue or cache mechanism may store one or more blocks and associated stamps so that the one or more blocks and associated stamps may be written to a hard disk drive at once. 
     An issue may arise in that different files may be modified at different times in the same block. For example, if at time T 1 , a file x.dat is modified in logical Block 1 , the system  100  may associate a stamp of T 1  with Block 1  and hold it in a queue or cache mechanism for later writing to the CDP system  130 . If a file y.dat, which shares the same logical Block 1  as x.dat, is modified at a time T 2 , then the system  100  may associate a stamp T 2  to Block 1 , even though Block 1  has not been transmitted to the CDP system  130 . A second issue may arise if the system  100  modifies the same block again after a first modification before the first modified block is transmitted to the CDP system  130 . For example, the system  100  may modify Block 1  and may associate it with a stamp of T 1 . Block 1  may be held in a queue or cache mechanism, but while it is in the queue or cache mechanism, the system  100  may modify Block 1  again, and the system  100  may associate a new stamp of T 2  to the twice-modified Block 1 . 
     One or more embodiments of the system  100  or method of the present disclosure may be operable to create one or more “shadow blocks” in order to maintain the integrity of the blocks and associated stamps. For example, if modified Block 1  is in a queue or cache mechanism, and the system  100  modifies Block 1  again, the system  100  may make a copy of Block 1  and the associated stamp in the queue or cache mechanism, so that either the original Block 1  or the copy of Block 1  may be modified and associated with a new stamp. 
     At this point it should be noted that the operation of a system and method in accordance with the present disclosure as described above typically involves the processing of input data and the generation of output data to some extent. This input data processing and output data generation may be implemented in hardware or software. For example, specific electronic components may be employed in a system or similar or related circuitry for implementing the functions associated with creating modified data blocks or transmitting them to storage or memory or to a CDP system in accordance with the present disclosure as described above. Alternatively, one or more processors operating in accordance with stored instructions may implement the functions associated with the system or the continuous data protection system in accordance with the present disclosure as described above. If such is the case, it is within the scope of the present disclosure that such instructions may be stored on one or more processor readable carriers (e.g., a magnetic disk or other storage medium), or transmitted to one or more processors via one or more signals embodied in one or more carrier waves. 
     The present disclosure is not to be limited in scope by the specific embodiments described herein. Indeed, other various embodiments of and modifications to the present disclosure, in addition to those described herein, will be apparent to those of ordinary skill in the art from the foregoing description and accompanying drawings. Thus, such other embodiments and modifications are intended to fall within the scope of the present disclosure. Further, although the present disclosure has been described herein in the context of a particular implementation in a particular environment for a particular purpose, those of ordinary skill in the art will recognize that its usefulness is not limited thereto and that the present disclosure may be beneficially implemented in any number of environments for any number of purposes. Accordingly, the claims set forth below should be construed in view of the full breadth and spirit of the present disclosure as described herein.