Patent Publication Number: US-10761760-B2

Title: Duplication between disparate deduplication systems

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present patent application is a continuation of U.S. patent application Ser. No. 15/953,608, filed on Apr. 16, 2018, now U.S. Pat. No. 10,318,203, entitled “Duplication Between Disparate Deduplication Systems”, which is a continuation of U.S. patent application Ser. No. 15/363,902, filed on Nov. 29, 2016, entitled “Duplication Between Disparate Deduplication Systems”, issued on Apr. 17, 2018 as U.S. Pat. No. 9,946,486, which are incorporated by reference herein in their entirety and for all purposes. 
    
    
     FIELD OF THE DISCLOSURE 
     This disclosure is related to deduplication backup systems. In particular, this disclosure is related to duplication between disparate deduplication systems. 
     DESCRIPTION OF THE RELATED ART 
     A fingerprinting algorithm is an algorithm that maps a file, data segments, or other unit of data to a more compact representation (e.g., resulting in a unique file identifier and/or data segment fingerprints, or the like). A fingerprint uniquely identifies the file and/or the file&#39;s data segments, and is typically used to avoid unnecessary storage, comparison, or transmission of excessive amounts of data. For example, a backup server can check whether a file has been modified by retrieving one or more fingerprint(s) and comparing the retrieved fingerprint(s) with a previously backed-up copy. Therefore, fingerprint(s) may be used for data deduplication. 
     Different deduplication systems can use different native fingerprint methodologies or algorithms. For example, a source deduplication system might use Message-Digest Algorithm 5 (MD5) fingerprint algorithm, whereas a target deduplication might use Secure Hash Algorithm 256 (SHA-256) fingerprint algorithm. 
     Optimizing the duplication of deduplicated data between such deduplication systems requires both deduplication systems to use the same fingerprint methodology or algorithm. If not, deduplicated data must be rehydrated using the source fingerprint algorithm, and then re-deduplicated using the target fingerprint algorithm. Obviously, such data migration is resource intensive, cumbersome, and inefficient. 
     SUMMARY OF THE DISCLOSURE 
     Disclosed herein are methods, systems, and processes to duplicate data between disparate deduplication systems. One such method involves generating, at a source deduplication system, source fingerprints for data blocks using a source fingerprint algorithm, and determining whether the data blocks are new or modified using the source fingerprint(s) generated for the data block(s) and previously-generated source fingerprints. 
     In this example, if a determination is made that the data blocks, or a subset thereof, are new or modified, the method generates target fingerprints for these new or modified data blocks using a target fingerprint algorithm associated with a target deduplication system, and sends the target fingerprint(s) to the target deduplication system. 
     In one embodiment, the method receives a request from the target deduplication system for one or more of the data blocks that are new or modified. Based on the request, the method sends the one or more of the data blocks that are new or modified to the target deduplication system. 
     In some embodiments, the previously-generated source fingerprints are generated using the source fingerprint algorithm, and the source fingerprint algorithm and the target fingerprint algorithm are different from one another. 
     In other embodiments, the method determines a reference count of the data blocks, and sends the reference count of the data blocks to the target deduplication system as part of sending the one or more of the data blocks that are new or modified. 
     In certain embodiments, the method accesses the target fingerprint algorithm associated with the target deduplication system from a computing system communicatively coupled to the source deduplication system, or receives the target fingerprint algorithm associated with the target deduplication system from the target deduplication system. 
     In one embodiment, the data blocks are deduplicated by the source deduplication system prior to the generation of the target fingerprint for one or more of the data blocks. 
     In certain embodiments, the method determines whether the data blocks have been previously sent to the target deduplication system. 
     In other embodiments, the method converts or translates the source fingerprint for one or more of the data blocks that are new or modified to the target fingerprint generated using the target fingerprint algorithm associated with the target deduplication system. 
     The foregoing is a summary and thus contains, by necessity, simplifications, generalizations and omissions of detail; consequently those skilled in the art will appreciate that the summary is illustrative only and is not intended to be in any limiting. Other aspects, features, and advantages of the present disclosure, as defined solely by the claims, will become apparent in the non-limiting detailed description set forth below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure may be better understood, and its numerous objects, features and advantages made apparent to those skilled in the art by referencing the accompanying drawings. 
         FIG. 1  is a block diagram of a computing system  100  that performs duplication between disparate deduplication systems, according to one embodiment of the present disclosure. 
         FIG. 2  is a block diagram of a computing system  200  that performs duplication between disparate deduplication systems, according to one embodiment of the present disclosure. 
         FIG. 3  is a fingerprint translation table  300 , according to one embodiment of the present disclosure. 
         FIG. 4  is a flowchart  400  that illustrates a process for performing duplication between disparate deduplication systems, according to one embodiment of the present disclosure. 
         FIG. 5  is a flowchart  500  that illustrates a process for sending target fingerprints from a source deduplication system to a target deduplication system, according to one embodiment of the present disclosure. 
         FIG. 6  is a flowchart  600  that illustrates a process for sending a fingerprint translation table from a source deduplication system to a target deduplication system, according to one embodiment of the present disclosure. 
         FIG. 7  is a flowchart  700  that illustrates a process for receiving target fingerprints from a source deduplication system at a target deduplication system, according to one embodiment of the present disclosure. 
         FIG. 8  is a block diagram of a computing system  800  that facilitates shared services between deduplication systems, according to one embodiment of the present disclosure. 
         FIG. 9  is a block diagram of a networking system  900 , according to one embodiment of the present disclosure. 
     
    
    
     While the disclosure is susceptible to various modifications and alternative forms, specific embodiments of the disclosure are provided as examples in the drawings and detailed description. It should be understood that the drawings and detailed description are not intended to limit the disclosure to the particular form disclosed. Instead, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the disclosure as defined by the appended claims. 
     DETAILED DESCRIPTION 
     Introduction 
     A fingerprinting algorithm is an algorithm that maps a larger data item (e.g., a computer file, data segment, or other unit of data) to a smaller value. The smaller value is sometimes referred to as the “fingerprint” of the data item. The fingerprint uniquely identifies the data item. During a backup, clients and/or computing systems can duplicate data within a set of data to be backed up. In addition, if a set of data is backed up multiple times, data that is unchanged or unmodified also results in duplicates of previously backed up data. In order to prevent backing up duplicate data from a client or multiple clients, backup systems can implement deduplication, which is a process for removing duplicate copies of data. Deduplication preserves storage space when backing up data from client systems. Data deduplicated by a source deduplication system can then be duplicated to a target deduplication system for disaster recovery purposes and the like. 
     Fingerprints may be used for data deduplication purposes, and so avoid the need for comparison and transmission of excessive amounts of data. For example, backup servers can check whether a file has been modified by retrieving only the file&#39;s fingerprint (instead of the entire file), and comparing the retrieved fingerprint with that of a previously-retrieved copy of the file. Thus, matching fingerprints in such a situation obviates the need to transfer the files. A fingerprint can also be a value generated for a given data segment. Typically, such fingerprint values are unique to each data segment, and thus distinguish data segments from one another. An example implementation of a fingerprint is a hash value. For example, hashing algorithms (also called fingerprinting algorithms) such as Rabin&#39;s Algorithm, Message-Digest Algorithm 5 (MD5), and Secure Hash Algorithm 512 (SHA-512), and the like, can be used to generate hash values. 
     As previously noted, different deduplication systems may use and implement different native fingerprint methodologies or algorithms for data deduplication. For example, a source deduplication system might use the MD5 fingerprint algorithm, whereas a target deduplication might use the SHA-256 or the SHA-512 fingerprint algorithm. Duplicating deduplicated data between such disparate deduplication systems presents unique challenges. 
     Optimized duplication between deduplication systems involves a source deduplication system sending a query to a target deduplication system to determine whether the target deduplication system has data fingerprinted by the source deduplication system. If the target (or destination) deduplication system has the data fingerprinted by the source deduplication system, then this data is not transferred (or migrated) by the source deduplication system during the optimized duplication process. However, this process works only if the source and target deduplication systems calculate or determine fingerprint values using the same fingerprint algorithm or methodology. If the source and target deduplication systems use different fingerprint algorithms or methodologies, optimized duplication does not work and regular (e.g., hydrated) duplication must occur. 
     In addition, requiring the modification of source and/or target deduplication systems in order to change the native (e.g., internal) deduplication implementations employed is cumbersome and cost ineffective, particularly if more than one such change becomes necessary. Disclosed herein are methods, systems, and processes to perform duplication between disparate deduplication systems without requiring such deduplication systems to change their own native (internal) deduplication implementations. 
     Example Computing Systems to Duplicate Data Between Disparate Deduplication Systems 
       FIG. 1  is a block diagram of a computing system  100  that can be configured to perform duplication or data migration between disparate deduplication systems, according to one embodiment. As shown in  FIG. 1 , clients  105 ( 1 )-(N) generate data that is deduplicated by source deduplication system  115  implemented in source backup server  110 . Clients  105 ( 1 )-(N) and source backup server  110  can be any of a variety of different types of computing devices, including a server, personal computing device, laptop computer, cellular phone, or the like. Source backup server  110  is communicatively coupled to target backup server  155  via network  185 . It will be appreciated that any type of network and/or interconnection other than network  185  (e.g., the Internet, a Local Area Network (LAN), and the like) can be used to facilitate communication between source deduplication system  115  and target deduplication system  160 . 
     As shown in  FIG. 1 , source deduplication system  115  includes a data block analyzer  120  and a source fingerprint generator  125 . Data block analyzer  120  analyzes data received from clients  105 ( 1 )-(N) (e.g., in the form of data segments or data blocks). For example, data block analyzer  120  can determine whether certain data blocks, data segments, or other units of data received from clients  105 ( 1 )-(N) are new or modified. 
     Source fingerprint generator  125  further implements a source fingerprint algorithm  130  and uses a target fingerprint algorithm  135 . In this example, source fingerprint algorithm  130  is a native (or internal) fingerprint algorithm or methodology implemented by source deduplication system  115 . In some embodiments, source fingerprint generator  125  can use more than one (non-native) target fingerprint algorithm (e.g., target fingerprint algorithms or methodologies associated with various different target deduplication systems). 
     Source deduplication system  115  is communicatively coupled to a source backup device  140 . Source backup device  140  stores data backed up and deduplicated by source deduplication system  115  in the form of a source backup image  145 . Source backup device  140  also includes source backup metadata  150 . Source backup metadata  150  contains information regarding data in source backup image  145  (e.g., the association between data blocks in source backup image  145  and one or more data objects such as files, and the like). Similarly, target deduplication system  160  is communicatively coupled to a target backup device  170 . Target backup device  170  stores data duplicated by source deduplication system  115  to target deduplication system  160  in the form of a target backup image  175 . Target backup device  170  also includes target backup metadata  180 . Target backup metadata  180  contains information regarding data in target backup image  175 . 
     It will be appreciated that source backup device  140  and target backup device  170  can include one or more of a variety of different storage devices, including hard disks, compact discs, digital versatile discs, one or more solid state drives (SSDs) memory such as Flash memory, and the like, or one or more logical storage devices such as volumes implemented on one or more such physical storage devices. 
       FIG. 2  is a block diagram of a computing system  200  that performs duplication between disparate deduplication systems, according to one embodiment. As shown in  FIG. 2 , in addition to data block analyzer  120  and source fingerprint generator  125 , source deduplication system  115  also implements and includes a fingerprint translation table  205 , a source reference generator  210 , and a source fingerprint database  215 . In addition, source backup device  140  stores multiple source backup images  145 ( 1 )-(N), as well as a source catalog  220 . 
     Source fingerprint generator  125  generates source fingerprints for data blocks received from clients  105 ( 1 )-(N) using source fingerprint algorithm  130  and stores these source fingerprints in source fingerprint database  215 . As noted, source fingerprint algorithm  130  is a native or internal fingerprint algorithm implemented by source deduplication system  115  and is used to deduplicate data received from clients  105 ( 1 )-(N). 
     Source deduplication system  115  can receive target fingerprint algorithm  135  (or an identifier thereof) from target deduplication system  160 , or can access target fingerprint algorithm  135  from some other computing system, database, storage device, and the like, that is part of network  190  (possibly using such an identifier). Target fingerprint algorithm  135  is a native or internal fingerprint algorithm implemented by target deduplication system  160  and is different than source fingerprint algorithm  130 . Therefore, target fingerprint algorithm  135  can be considered non-native to source deduplication system  160  and thus, cannot be used by source deduplication system  160  to deduplicate data received from clients  105 ( 1 )-(N). 
     Also as shown in  FIG. 2 , and in addition to target fingerprint generator  165 , target deduplication system  160  includes a fingerprint receiver  225 , a target reference generator  230 , and a target fingerprint database  235 . Fingerprint receiver  225  receives target fingerprints generated on the fly by source fingerprint generator  125  using target fingerprint algorithm  135 , and determines whether those (received) target fingerprints are present in target fingerprint database  235 . In addition, target backup device  170  stores multiple target backup images  175 ( 1 )-(N), as well as a target catalog  240 . Target backup images  175 ( 1 )-(N) contain data duplicated to target deduplication  160  by source deduplication system  115 . 
     In one embodiment, source fingerprint generator  125  generates source fingerprints at source deduplication system  115  for data blocks (e.g., received from clients  105 ( 1 )-(N)) using source fingerprint algorithm  130 . Data block analyzer  120  then determines whether the data blocks are new or modified, using the source fingerprints generated for the data blocks and previously-generated source fingerprints. For example, data block analyzer  120  can compare the source fingerprint generated for each data block (e.g., by source fingerprint generator  125  using source fingerprint algorithm  130 ) with previously-generated source fingerprints (e.g., also generated using source fingerprint algorithm  130 ) in source fingerprint database  215  to determine whether one or more of the newly generated source fingerprints match previously-generated fingerprints in source fingerprint database  215 . In this manner, data block analyzer  120  can determine whether a given data block is new or modified (obviously, the opposite could be determined, in the alternative, such that a determination as to whether or not a data block were existing and unchanged could be made). 
     In some embodiments, if a determination is made that a given data block is new or modified (e.g., the source fingerprint generated for the data block using source fingerprint algorithm  130  does not match previously-generated fingerprints in source fingerprint database  215 ), source fingerprint generator generates a target fingerprint for the data block using target fingerprint algorithm  135 . In some examples, source fingerprint generator  210  then sends the target fingerprint for the data block directly to target deduplication system  160 . In other examples, source fingerprint generator  210  creates and populates fingerprint translation table  205  with the target fingerprint, and sends fingerprint translation table  205  to target deduplication system  160 . In certain embodiments, fingerprint receiver  225  receives one or more target fingerprints generated by source fingerprint generator  125  using target fingerprint algorithm  135 . Fingerprint receiver  225  then determines whether the (received) target fingerprints (e.g., for one or more new or modified data blocks) are part of target fingerprint database  235 . If the target fingerprint(s) received from source deduplication  115  are not part of target fingerprint database  235 , target deduplication system  160  sends a request to source deduplication system  115  for data block(s) associated with those target fingerprint(s) that are not part of target fingerprint database  235 . Such a request can be sent by target deduplication system  160  in various manners. 
     In one example, target deduplication system  160  can simply return the target fingerprint(s) sent by source deduplication system  115  to source deduplication system  115  if those target fingerprint(s) are not part of target fingerprint database  235 . In this case, source deduplication  115  can identify and send the data block(s) that correspond to the target fingerprint(s) sent back by target deduplication system  160 . In another example, target deduplication system  160  can identify the data block that corresponds to a particular target fingerprint and request that data block from source deduplication system  115 . 
     Therefore, based on target fingerprint(s) generated by source deduplication system  115  using target fingerprint algorithm  135 , and sent to target deduplication system  160  by source deduplication system  115 , source deduplication system  115  receives a request from target deduplication system  160  for one or more data blocks that are new or modified. Based on this request, source deduplication system  115  sends those requested data blocks (e.g., that are new or modified) to target deduplication system  160 . 
     In some embodiments, data block analyzer  120  can determine that certain data blocks are not new or modified (i.e., existing and unchanged). For example, a source fingerprint calculated for a data block by source fingerprint generator  125  using source fingerprint algorithm  130  can be present in source fingerprint database  215 . In such circumstances, source reference generator  210  simply increments the reference count of the data block and updates source catalog  220  (e.g., to indicate that the data block is not new or modified, but has been accessed again). However, because this data block is not new or modified, there is no need to duplicate this data block to target deduplication system  160 . In such cases, source deduplication system  115  simply sends the (updated) reference count of the data block to target deduplication system  160  (e.g., to update target catalog  240 ) as part of sending one or more data blocks that are new or modified. 
     Therefore, source deduplication system  115  converts or translates the source fingerprint for one or more of the data blocks that are new or modified to the target fingerprint generated using target fingerprint algorithm  135  associated with the target deduplication system  160 , and performs duplication without requiring target deduplication system  160  to change its own deduplication fingerprint methodology. 
     Examples of Performing On The Fly Translation of Fingerprints For Duplication 
       FIG. 3  is an example table  300 , according to one embodiment. Fingerprint translation table  205  includes a client field  305 , a file field  310 , a data block field  315 , a reference count field  320 , a source fingerprint field  325 , a target fingerprint field  330 , and a duplicate field  335 . In certain embodiments, fingerprint translation table  205  can be used by source deduplication system  115  to duplicate data to target deduplication system  160 . 
     For example, client  105 ( 1 ) can generate a data block A that is part of file Project 1 with a reference count of 2. Source fingerprint generator  125  first generates a source fingerprint for data block A using source fingerprint algorithm  130  (e.g., sdfg7890). If the source fingerprint for data block A is not present in source fingerprint database  215 , source fingerprint generator  125  generates a target fingerprint for data block A on the fly using target fingerprint algorithm  135  (e.g., asdf1234). Source deduplication system  115  then sends fingerprint translation table  205  to target deduplication system  160  or, in certain embodiments, just sends the target fingerprint (e.g., asdf1234) to target fingerprint receiver  225  to “check” whether target deduplication system  160  has a target fingerprint in target fingerprint database  235  that matches asdf1234 (e.g., because data block A has a reference count of 2—indicating that data block A has been previously accessed, and therefore, may not be new to target deduplication system  160 ). As previously noted, source deduplication system  115  either receives a request for a data block that corresponds to asdf1234 from target deduplication system  160 , or in certain embodiments, receives the actual/sent target fingerprint (e.g., asdf1234) back from target deduplication system  160 . Source deduplication system  115  then sends or transfers data block A to target deduplication  160 . 
     In some embodiments, it will be appreciated that fingerprint translation table  205  can be useful to keep track of data blocks that are new, thus permitting source deduplication system  115  to duplicate such a data block to target deduplication system  160  without requiring target deduplication system  160  to check whether the target fingerprint for the data block exists in target fingerprint database  235 . One such example is provided with reference to data block M shown in fingerprint translation table  205 . 
     Client  105 ( 1 ) can generate a data block M that is part of a file Project 1 and has a reference count of 1. Source fingerprint generator  125  first generates a source fingerprint for data block M using source fingerprint algorithm  130  (e.g., ghjk1234). If the source fingerprint for data block M is not present in source fingerprint database  215 , source fingerprint generator  125  generates a target fingerprint for data block M on the fly using target fingerprint algorithm  135  (e.g., wert5678). Source deduplication system  115  then updates fingerprint translation table  205  (e.g., duplicate field  335 ) to indicate that because data block M is new to source deduplication system  115 , data block M is has also not been likely duplicated to target deduplication system  160 . In this case, there is no need for target deduplication system  160  to check whether the target fingerprint for data block M (e.g., wert5678) is present in target fingerprint database  235 . Data block M can be duplicated to target deduplication system  160  next time source deduplication system  115  performs a deduplication operation. In addition, because the target fingerprint for data block M has already been calculated by source deduplication system  115 , target deduplication system  160  does not need to separately calculate the target fingerprint for data block M, thus saving valuable computing resources during duplication operations between disparate deduplication systems. 
     As previously noted, in addition to sending new or modified data blocks to target deduplication system  160  as part of deduplication operations, source deduplication system  115  can also send instructions to target deduplication system  160  to update the reference counts of particular data blocks that are not new or modified (e.g., for data blocks containing data that has already been encountered, and so for which a fingerprint already exists). One such example is provided with reference to data block B shown in fingerprint translation table  205 . As shown in fingerprint translation table  205 , data block B is part of file Project 2. Initially, data block B has a reference count of 1 and is duplicated to target deduplication system  160  based on target fingerprint zxcv3456. However, if source deduplication system  115  analyzes data block B a second time and data block B is not modified, source deduplication system  115  simply increments the reference count of data block B to 2 and instructs target deduplication system  160  to do the same. As previously noted, this update to the reference count of data block B can be sent to target deduplication system  160  as part of sending new or modified data blocks. 
     Therefore, in this manner, fingerprint translation table  205  can be used by source deduplication system  115  to perform on the fly fingerprint translation or conversion between source and target fingerprints for a given data block or data segment. Among various other functions, on the fly translation or conversion of source fingerprints into target fingerprints for data blocks as shown in fingerprint translation table  205  can be used to: (1) check whether a data block has been previously sent to target deduplication system  160  as part of a previous duplication operation either by source deduplication system  115  or by some other computing system, (2) send new or modified blocks to target deduplication system  160  by pre-calculating the new or modified data blocks&#39; target fingerprints, and (3) update reference counts, target backup metadata  180  and target catalog  240  as part of performing duplication operations (e.g., so that data can be rehydrated efficiently by target deduplication system  160 ). 
     Example Processes to Duplicate Data Between Disparate Deduplication Systems 
       FIG. 4  is a flowchart  400  that illustrates a process for performing duplication between disparate deduplication systems, according to one embodiment. The process begins at  410  by generating source fingerprint(s) for data block(s) (e.g., data blocks received and analyzed by data block analyzer  120 ). At  420 , the process determines whether the data block(s) are new or modified, or whether the source fingerprint(s) calculated for the data block(s) (e.g., using source fingerprint algorithm  130 ) do not match existing source fingerprints (e.g., previously-generated source fingerprints in source fingerprint database  215 ). 
     If the data block(s) are not new or modified, or the source fingerprint(s) calculated for the data block(s) match existing source fingerprints, the process ends (e.g., source deduplication system  160  simply increments the reference count of the data block(s) and updates source catalog  220 ). Otherwise, the process proceeds to  430  where target fingerprint(s) for the data block(s) are generated (e.g., using target fingerprint algorithm  135 ). At  440 , the process sends the target fingerprint(s) to target deduplication system  440 . As previously noted, the target fingerprint(s) can be sent to fingerprint receiver  225  directly (e.g., target fingerprints asdf1234, wert5678, and the like), or as part of fingerprint translation table  205 , as shown in  FIG. 3 . 
     At  450 , the process receives a request for one or more data blocks. As previously noted, source deduplication system  115  can receive one or more target fingerprint(s) sent to target deduplication system  160  back from target deduplication system  160 , or source deduplication system  115  can receive a request for particular data blocks associated with particular target fingerprints. For example, if source deduplication system  115  sends  10  target fingerprints to target deduplication system  160 , source deduplication system  115  can receive a request for data block(s) associated with target fingerprints  2 ,  5 , and  8  (out of the 10 sent to target deduplication system  160 ) from target deduplication system  160 . Regardless of which method is used, source deduplication system  115  can identify the data block(s) associated with the target fingerprint(s) that are not part of target fingerprint database  235  (e.g., as determined by target deduplication system  160 ). 
     At  460 , the process sends (e.g., transmits or copies) the requested data block(s) to target deduplication system  160 . At  470 , the process determines whether there are additional data block(s) to process. If there are more data blocks to process, the process loops back to  410 . Otherwise, the process ends. 
       FIG. 5  is a flowchart  500  that illustrates a process for sending target fingerprints from a source deduplication system to a target deduplication system, according to one embodiment. The process begins at  510  by receiving data block(s) (e.g., from clients  105 ( 1 )-(N)). At  520 , the process generates source fingerprints(s) for the data block(s) using source fingerprint algorithm  130 . In this example, source fingerprint algorithm  130  is a native or internal fingerprint algorithm of source deduplication system  115  and is used by source deduplication system  115  to perform data deduplication operations. 
     At  530 , the process identifies new or modified data block(s) using the source fingerprint(s) (e.g., by comparing source fingerprint(s) to previously-generated source fingerprint(s) in source fingerprint database  215  to determine if there is a match). At  540 , the process generates target fingerprint(s) for new or modified data block(s) using target fingerprint algorithm  135  (e.g., a non-native and different fingerprint algorithm). 
     At  550 , the process sends the target fingerprint(s) of new or modified blocks to target deduplication system  160  (e.g., either on their own or as part of fingerprint translation table  205 ). At  560 , the process receives a request for one or more new or modified data blocks from target deduplication system  160 . The process receives such a request only if target deduplication system  160  determines that the one or more new or modified data blocks are not present in target fingerprint database  235 . If the one or more new or modified data blocks were determined by target deduplication system  160  to be present in target fingerprint database  235 , then such a request would simply request metadata associated with those one or more data blocks (e.g., (updated) reference counts, and the like) from source deduplication system  115  (e.g., so that target deduplication system  160  can update target catalog  240  with the latest information about the one or more data blocks for efficient rehydration of data). 
     At  570 , the process sends the requested new or modified data block(s) to target deduplication system  160 . As previously noted, the request from target deduplication  160  can simply include a list of previously-sent target fingerprints that are not present in target fingerprint database  235 . Alternatively, the request can identify and request data block(s) associated with a subset of target fingerprint(s) of target fingerprint(s) sent to target deduplication system  160  by source deduplication system  115 ). At  580 , the process determines whether there are more data block(s) to process. If there are more data blocks to process, the process loops back to  510 . Otherwise, the process ends. 
       FIG. 6  is a flowchart  600  that illustrates a process for sending a fingerprint translation table from a source deduplication system to a target deduplication system, according to one embodiment. The process begins at  610  by receiving data blocks from clients (e.g., clients  105 ( 1 )-(N)). At  620 , the process generates source fingerprint(s) for the data block(s). At  630 , the process determines whether the data block(s) are new or modified, or whether the source fingerprint(s) calculated for the data block(s) (e.g., using source fingerprint algorithm  130 ) matches existing source fingerprints (e.g., previously-generated source fingerprints in source fingerprint database  215 ). 
     If the data block(s) are not new or modified, or the source fingerprint(s) calculated for the data block(s) match existing source fingerprints, the process ends (e.g., source deduplication system  160  simply increments the reference count of the data block(s) and updates source catalog  220 ). However, if the data block(s) are new or modified, or the source fingerprint(s) calculated for the data block(s) do not match existing source fingerprints, the process, at  640 , accesses or receives target fingerprint algorithm  135  (e.g., from target deduplication system  160  or some other computing system communicatively coupled to network  185 ). 
     At  650 , the process generates target fingerprint(s) for data block(s) is they are new or modified, or if the data block(s) do not match existing source fingerprint(s). At  660 , the process populates fingerprint translation table  205  with target fingerprint(s) (e.g., as shown in  FIG. 3 ). At  670 , the process sends fingerprint translation table  205  to target deduplication system  160 . At  680 , the process determines whether there are more data block(s) to process. If there are more data blocks to process, the process loops back to  610 . Otherwise, the process ends. 
       FIG. 7  is a flowchart  700  that illustrates a process for receiving target fingerprints from a source deduplication system at a target deduplication system, according to one embodiment. The process begins at  710  by receiving target fingerprint(s) from source deduplication system  115  (e.g., on their own or as part of fingerprint translation table  205 ). At  720 , the process identifies received target fingerprint(s) not in target fingerprint database  235 . At  730 , the process requests data block(s) corresponding to received target fingerprint(s) not in target fingerprint database  235  from source deduplication system  160  (e.g., by sending back target fingerprint(s) not in target fingerprint database  235  to source deduplication system  160 ). 
     At  740 , the process receives the requested data block(s) from source deduplication system  115 . At  750 , the process stores the data block(s) received from source deduplication system  115  (e.g., on target backup device  170 ), and at  760 , updates target catalog  240 . At  770 , the process determines whether there are more target fingerprint(s) received from source deduplication system  115 . If there are more target fingerprint(s) received, the process loops back to  710 . Otherwise, the process ends. 
     Example Computing System 
       FIG. 8  is a block diagram of a computing system  800  that facilitates duplication and/or data migration between disparate deduplication systems, according to one embodiment. Computing system  800  broadly represents any single or multi-processor computing device or system capable of executing computer-readable instructions. Examples of computing system  800  include, without limitation, any one or more of a variety of devices including workstations, personal computers, laptops, client-side terminals, servers, distributed computing systems, handheld devices (e.g., personal digital assistants and mobile phones), network appliances, storage controllers (e.g., array controllers, tape drive controller, or hard drive controller), and the like. In its most basic configuration, computing system  800  may include at least one processor  855  and a memory  860 . By executing the software that implements source deduplication system  115  and/or target deduplication system  160 , computing system  800  becomes a special purpose computing device that is configured to duplicate data between disparate deduplication systems. 
     Processor  855  generally represents any type or form of processing unit capable of processing data or interpreting and executing instructions. In certain embodiments, processor  855  may receive instructions from a software application or module. These instructions may cause processor  855  to perform the functions of one or more of the embodiments described and/or illustrated herein. For example, processor  855  may perform and/or be a means for performing all or some of the operations described herein. Processor  855  may also perform and/or be a means for performing any other operations, methods, or processes described and/or illustrated herein. 
     Memory  860  generally represents any type or form of volatile or non-volatile storage devices or mediums capable of storing data and/or other computer-readable instructions. Examples include, without limitation, random access memory (RAM), read only memory (ROM), flash memory, or any other suitable memory device. Although not required, in certain embodiments computing system  800  may include both a volatile memory unit and a non-volatile storage device. In one example, program instructions implementing a source fingerprint generator  125  and/or a fingerprint translation table  205  may be loaded into memory  860 . 
     In certain embodiments, computing system  800  may also include one or more components or elements in addition to processor  855  and/or memory  860 . For example, as illustrated in  FIG. 8 , computing system  800  may include a memory controller  820 , an Input/Output (I/O) controller  835 , and a communication interface  845 , each of which may be interconnected via a communication infrastructure  805 . Communication infrastructure  805  generally represents any type or form of infrastructure capable of facilitating communication between one or more components of a computing device. Examples of communication infrastructure  805  include, without limitation, a communication bus (such as an Industry Standard Architecture (ISA), Peripheral Component Interconnect (PCI), PCI express (PCIe), or similar bus) and a network. 
     Memory controller  820  generally represents any type/form of device capable of handling memory or data or controlling communication between one or more components of computing system  800 . In certain embodiments memory controller  820  may control communication between processor  855 , memory  860 , and I/O controller  835  via communication infrastructure  805 . In certain embodiments, memory controller  820  may perform and/or be a means for performing, either alone or in combination with other elements, one or more of the operations or features described and/or illustrated herein. 
     I/O controller  835  generally represents any type or form of module capable of coordinating and/or controlling the input and output functions of a virtualization server and/or a computing device. For example, in certain embodiments I/O controller  835  may control or facilitate transfer of data between one or more elements of computing system  800 , such as processor  855 , memory  860 , communication interface  845 , display adapter  815 , input interface  825 , and storage interface  840 . 
     Communication interface  845  broadly represents any type or form of communication device or adapter capable of facilitating communication between computing system  800  and one or more other devices. Communication interface  845  may facilitate communication between computing system  800  and a private or public network including additional computing systems. Examples of communication interface  845  include, without limitation, a wired network interface (such as a network interface card), a wireless network interface (such as a wireless network interface card), a modem, and any other suitable interface. Communication interface  845  may provide a direct connection to a remote server via a direct link to a network, such as the Internet, and may also indirectly provide such a connection through, for example, a local area network (e.g., an Ethernet network), a personal area network, a telephone or cable network, a cellular telephone connection, a satellite data connection, or any other suitable connection. 
     Communication interface  845  may also represent a host adapter configured to facilitate communication between computing system  800  and one or more additional network or storage devices via an external bus or communications channel. Examples of host adapters include, Small Computer System Interface (SCSI) host adapters, Universal Serial Bus (USB) host adapters, Institute of Electrical and Electronics Engineers (IEEE) 1394 host adapters, Serial Advanced Technology Attachment (SATA), Serial Attached SCSI (SAS), and external SATA (eSATA) host adapters, Advanced Technology Attachment (ATA) and Parallel ATA (PATA) host adapters, Fibre Channel interface adapters, Ethernet adapters, or the like. Communication interface  845  may also allow computing system  800  to engage in distributed or remote computing (e.g., by receiving/sending instructions to/from a remote device for execution). 
     As illustrated in  FIG. 8 , computing system  800  may also include at least one display device  810  coupled to communication infrastructure  805  via a display adapter  815 . Display device  810  generally represents any type or form of device capable of visually displaying information forwarded by display adapter  815 . Similarly, display adapter  815  generally represents any type or form of device configured to forward graphics, text, and other data from communication infrastructure  805  (or from a frame buffer, as known in the art) for display on display device  810 . Computing system  800  may also include at least one input device  830  coupled to communication infrastructure  805  via an input interface  825 . Input device  830  generally represents any type or form of input device capable of providing input, either computer or human generated, to computing system  800 . Examples of input device  830  include a keyboard, a pointing device, a speech recognition device, or any other input device. 
     Computing system  800  may also include storage device  850  coupled to communication infrastructure  805  via a storage interface  840 . Storage device  850  generally represents any type or form of storage devices or mediums capable of storing data and/or other computer-readable instructions. For example, storage device  850  may include a magnetic disk drive (e.g., a so-called hard drive), a floppy disk drive, a magnetic tape drive, an optical disk drive, a flash drive, or the like. Storage interface  840  generally represents any type or form of interface or device for transferring and/or transmitting data between storage device  850 , and other components of computing system  800 . Storage device  850  may be configured to read from and/or write to a removable storage unit configured to store computer software, data, or other computer-readable information. Examples of suitable removable storage units include a floppy disk, a magnetic tape, an optical disk, a flash memory device, or the like. Storage device  850  may also include other similar structures or devices for allowing computer software, data, or other computer-readable instructions to be loaded into computing system  800 . For example, storage device  850  may be configured to read and write software, data, or other computer-readable information. Storage device  850  may also be a part of computing system  800  or may be separate devices accessed through other interface systems. 
     Many other devices or subsystems may be connected to computing system  800 . Conversely, all of the components and devices illustrated in  FIG. 8  need not be present to practice the embodiments described and/or illustrated herein. The devices and subsystems referenced above may also be interconnected in different ways from that shown in  FIG. 8 . 
     Computing system  800  may also employ any number of software, firmware, and/or hardware configurations. For example, one or more of the embodiments disclosed herein may be encoded as a computer program (also referred to as computer software, software applications, computer-readable instructions, or computer control logic) on a computer-readable storage medium. Examples of computer-readable storage media include magnetic-storage media (e.g., hard disk drives and floppy disks), optical-storage media (e.g., CD- or DVD-ROMs), electronic-storage media (e.g., solid-state drives and flash media), and the like. Such computer programs can also be transferred to computing system  800  for storage in memory via a network such as the Internet or upon a carrier medium. 
     The computer-readable medium containing the computer program may be loaded into computing system  800 . All or a portion of the computer program stored on the computer-readable medium may then be stored in memory  860  and/or various portions of storage device  850 . When executed by processor  855 , a computer program loaded into computing system  800  may cause processor  855  to perform and/or be a means for performing the functions of one or more of the embodiments described and/or illustrated herein. Additionally or alternatively, one or more of the embodiments described and/or illustrated herein may be implemented in firmware and/or hardware. For example, computing system  800  may be configured as an application specific integrated circuit (ASIC) adapted to implement one or more of the embodiments disclosed herein. 
     Example Networking System 
       FIG. 9  is a block diagram of a networking system  900 , according to one embodiment. In certain embodiments, network-attached storage (NAS) devices may be configured to communicate with source deduplication systems  115 ( 1 )-(N) and/or target deduplication systems  160 ( 1 )-(N) using various protocols, such as Network File System (NFS), Server Message Block (SMB), or Common Internet File System (CIFS). Network  185  generally represents any type or form of computer network or architecture capable of facilitating communication between source deduplication systems  115 ( 1 )-(N) and/or target deduplication systems  160 ( 1 )-(N). In certain embodiments, a communication interface, such as communication interface  845  in  FIG. 8 , may be used to provide connectivity between source deduplication systems  115 ( 1 )-(N) and/or target deduplication systems  160 ( 1 )-(N), and network  185 . It should be noted that the embodiments described and/or illustrated herein are not limited to the Internet or any particular network-based environment. For example, network  185  can be a Storage Area Network (SAN). 
     In one embodiment, all or a portion of one or more of the disclosed embodiments may be encoded as a computer program and loaded onto and executed by the duplication system  910 , source deduplication systems  115 ( 1 )-(N), and/or target deduplication systems  160 ( 1 )-(N), or any combination thereof. All or a portion of one or more of the embodiments disclosed herein may also be encoded as a computer program, stored on duplication system  910 , source deduplication systems  115 ( 1 )-(N), and/or target deduplication systems  160 ( 1 )-(N), and distributed over network  185 . In some examples, all or a portion of duplication system  910 , source deduplication systems  115 ( 1 )-(N), and/or target deduplication systems  160 ( 1 )-(N) may represent portions of a cloud-computing or network-based environment. Cloud-computing environments may provide various services and applications via the Internet. These cloud-based services (e.g., software as a service, platform as a service, infrastructure as a service, etc.) may be accessible through a web browser or other remote interface. 
     Various functions described herein may be provided through a remote desktop environment or any other cloud-based computing environment. In addition, one or more of the components described herein may transform data, physical devices, and/or representations of physical devices from one form to another. For example, duplication system  910 , source backup server  110 , and/or target backup server  155  may transform the behavior of source deduplication systems  115 ( 1 )-(N) and/or target deduplication systems  160 ( 1 )-(N) in order to cause source deduplication systems  115 ( 1 )-(N) and/or target deduplication systems  160 ( 1 )-(N) to perform duplication and/or data migration between disparate deduplication systems. 
     Although the present disclosure has been described in connection with several embodiments, the disclosure is not intended to be limited to the specific forms set forth herein. On the contrary, it is intended to cover such alternatives, modifications, and equivalents as can be reasonably included within the scope of the disclosure as defined by the appended claims.