Validating stored encoded data slice integrity in a dispersed storage network

An encoded data slice is received for storage by a dispersed storage and task (DST) execution unit. A plurality of initial integrity values are generated by executing a plurality of integrity check algorithms on the encoded data slice. The encoded data slice and the plurality of initial integrity values are stored in a memory of the DST execution unit. A subset of the plurality of integrity check algorithms are selected in response to a request to retrieve the encoded data slice. At least one final integrity value is generated by executing the subset of the plurality of integrity check algorithms on the encoded data slice stored in memory. An integrity status is generated by comparing the at least one final integrity value to the corresponding subset of the plurality of initial integrity values.

Not Applicable

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BACKGROUND OF THE INVENTION

Technical Field of the Invention

Aspects of this invention relate generally to computer networks and more particularly to dispersed storage of data and distributed task processing of data.

Description of Related Art

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1is a schematic block diagram of an embodiment of a distributed computing system10that includes a user device12and/or a user device14, a distributed storage and/or task (DST) processing unit16, a distributed storage and/or task network (DSTN) managing unit18, a DST integrity processing unit20, and a distributed storage and/or task network (DSTN) module22. The components of the distributed computing system10are coupled via a network24, which may include one or more wireless and/or wire lined communication systems; one or more non-public intranet systems and/or public internet systems; and/or one or more local area networks (LAN) and/or wide area networks (WAN). Hereafter, the distributed computing system10may be interchangeably referred to as a dispersed storage network (DSN).

The DSTN module22includes a plurality of distributed storage and/or task (DST) execution units36that may be located at geographically different sites (e.g., one in Chicago, one in Milwaukee, etc.). Each of the DST execution units is operable to store dispersed error encoded data and/or to execute, in a distributed manner, one or more tasks on data. The tasks may be a simple function (e.g., a mathematical function, a logic function, an identify function, a find function, a search engine function, a replace function, etc.), a complex function (e.g., compression, human and/or computer language translation, text-to-voice conversion, voice-to-text conversion, etc.), multiple simple and/or complex functions, one or more algorithms, one or more applications, etc. Hereafter, the DST execution unit may be interchangeably referred to as a storage unit and a set of DST execution units may be interchangeably referred to as a set of storage units.

Each of the user devices12-14, the DST processing unit16, the DSTN managing unit18, and the DST integrity processing unit20include a computing core26and may be a portable computing device and/or a fixed computing device. A portable computing device may be a social networking device, a gaming device, a cell phone, a smart phone, a digital assistant, a digital music player, a digital video player, a laptop computer, a handheld computer, a tablet, a video game controller, and/or any other portable device that includes a computing core. A fixed computing device may be a personal computer (PC), a computer server, a cable set-top box, a satellite receiver, a television set, a printer, a fax machine, home entertainment equipment, a video game console, and/or any type of home or office computing equipment. User device12and DST processing unit16are configured to include a DST client module34.

With respect to interfaces, each interface30,32, and33includes software and/or hardware to support one or more communication links via the network24indirectly and/or directly. For example, interface30supports a communication link (e.g., wired, wireless, direct, via a LAN, via the network24, etc.) between user device14and the DST processing unit16. As another example, interface32supports communication links (e.g., a wired connection, a wireless connection, a LAN connection, and/or any other type of connection to/from the network24) between user device12and the DSTN module22and between the DST processing unit16and the DSTN module22. As yet another example, interface33supports a communication link for each of the DSTN managing unit18and DST integrity processing unit20to the network24.

The distributed computing system10is operable to support dispersed storage (DS) error encoded data storage and retrieval, to support distributed task processing on received data, and/or to support distributed task processing on stored data. In general and with respect to DS error encoded data storage and retrieval, the distributed computing system10supports three primary operations: storage management, data storage and retrieval, and data storage integrity verification. In accordance with these three primary functions, data can be encoded (e.g., utilizing an information dispersal algorithm (IDA), utilizing a dispersed storage error encoding process), distributedly stored in physically different locations, and subsequently retrieved in a reliable and secure manner. Hereafter, distributedly stored may be interchangeably referred to as dispersed stored. Such a system is tolerant of a significant number of failures (e.g., up to a failure level, which may be greater than or equal to a pillar width (e.g., an IDA width of the IDA) minus a decode threshold minus one) that may result from individual storage device (e.g., DST execution unit36) failures and/or network equipment failures without loss of data and without the need for a redundant or backup copy. Further, the distributed computing system10allows the data to be stored for an indefinite period of time without data loss and does so in a secure manner (e.g., the system is very resistant to unauthorized attempts at accessing the data).

The second primary function (i.e., distributed data storage and retrieval) begins and ends with a user device12-14. For instance, if a second type of user device14has data40to store in the DSTN module22, it sends the data40to the DST processing unit16via its interface30. The interface30functions to mimic a conventional operating system (OS) file system interface (e.g., network file system (NFS), flash file system (FFS), disk file system (DFS), file transfer protocol (FTP), web-based distributed authoring and versioning (WebDAV), etc.) and/or a block memory interface (e.g., small computer system interface (SCSI), internet small computer system interface (iSCSI), etc.). In addition, the interface30may attach a user identification code (ID) to the data40.

To support storage management, the DSTN managing unit18performs DS management services. One such DS management service includes the DSTN managing unit18establishing distributed data storage parameters (e.g., vault creation, distributed storage parameters, security parameters, billing information, user profile information, etc.) for a user device12-14individually or as part of a group of user devices. For example, the DSTN managing unit18coordinates creation of a vault (e.g., a virtual memory block associated with a portion of an overall namespace of the DSN) within memory of the DSTN module22for a user device, a group of devices, or for public access and establishes per vault dispersed storage (DS) error encoding parameters for a vault. The DSTN managing unit18may facilitate storage of DS error encoding parameters for each vault of a plurality of vaults by updating registry information for the distributed computing system10. The facilitating includes storing updated system registry information in one or more of the DSTN module22, the user device12, the DST processing unit16, and the DST integrity processing unit20.

The DSTN managing unit18creates and stores user profile information (e.g., an access control list (ACL)) in local memory and/or within memory of the DSTN module22. The user profile information includes authentication information, permissions, and/or the security parameters. The security parameters may include encryption/decryption scheme, one or more encryption keys, key generation scheme, and/or data encoding/decoding scheme.

Another DS management service includes the DSTN managing unit18performing network operations, network administration, and/or network maintenance. Network operations includes authenticating user data allocation requests (e.g., read and/or write requests), managing creation of vaults, establishing authentication credentials for user devices, adding/deleting components (e.g., user devices, DST execution units, and/or DST processing units) from the distributed computing system10, and/or establishing authentication credentials for DST execution units36. Network administration includes monitoring devices and/or units for failures, maintaining vault information, determining device and/or unit activation status, determining device and/or unit loading, and/or determining any other system level operation that affects the performance level of the system10. Network maintenance includes facilitating replacing, upgrading, repairing, and/or expanding a device and/or unit of the system10.

To support data storage integrity verification within the distributed computing system10, the DST integrity processing unit20performs rebuilding of ‘bad’ or missing encoded data slices. At a high level, the DST integrity processing unit20performs rebuilding by periodically attempting to retrieve/list encoded data slices, and/or slice names of the encoded data slices, from the DSTN module22. For retrieved encoded slices, they are checked for errors due to data corruption, outdated version, etc. If a slice includes an error, it is flagged as a ‘bad’ slice. For encoded data slices that were not received and/or not listed, they are flagged as missing slices. Bad and/or missing slices are subsequently rebuilt using other retrieved encoded data slices that are deemed to be good slices to produce rebuilt slices. The rebuilt slices are stored in memory of the DSTN module22. Note that the DST integrity processing unit20may be a separate unit as shown, it may be included in the DSTN module22, it may be included in the DST processing unit16, and/or distributed among the DST execution units36.

Each slice name is unique to a corresponding encoded data slice and includes multiple fields associated with the overall namespace of the DSN. For example, the fields may include a pillar number/pillar index, a vault identifier, an object number uniquely associated with a particular file for storage, and a data segment identifier of a plurality of data segments, where the particular file is divided into the plurality of data segments. For example, each slice name of a set of slice names corresponding to a set of encoded data slices that has been dispersed storage error encoded from a common data segment varies only by entries of the pillar number field as each share a common vault identifier, a common object number, and a common data segment identifier.

To support distributed task processing on received data, the distributed computing system10has two primary operations: DST (distributed storage and/or task processing) management and DST execution on received data. With respect to the storage portion of the DST management, the DSTN managing unit18functions as previously described. With respect to the tasking processing of the DST management, the DSTN managing unit18performs distributed task processing (DTP) management services. One such DTP management service includes the DSTN managing unit18establishing DTP parameters (e.g., user-vault affiliation information, billing information, user-task information, etc.) for a user device12-14individually or as part of a group of user devices.

Another DTP management service includes the DSTN managing unit18performing DTP network operations, network administration (which is essentially the same as described above), and/or network maintenance (which is essentially the same as described above). Network operations include, but are not limited to, authenticating user task processing requests (e.g., valid request, valid user, etc.), authenticating results and/or partial results, establishing DTP authentication credentials for user devices, adding/deleting components (e.g., user devices, DST execution units, and/or DST processing units) from the distributed computing system, and/or establishing DTP authentication credentials for DST execution units.

To support distributed task processing on stored data, the distributed computing system10has two primary operations: DST (distributed storage and/or task) management and DST execution on stored data. With respect to the DST execution on stored data, if the second type of user device14has a task request38for execution by the DSTN module22, it sends the task request38to the DST processing unit16via its interface30. With respect to the DST management, it is substantially similar to the DST management to support distributed task processing on received data.

The DSTN interface module76functions to mimic a conventional operating system (OS) file system interface (e.g., network file system (NFS), flash file system (FFS), disk file system (DFS), file transfer protocol (FTP), web-based distributed authoring and versioning (WebDAV), etc.) and/or a block memory interface (e.g., small computer system interface (SCSI), internet small computer system interface (iSCSI), etc.). The DSTN interface module76and/or the network interface module70may function as the interface30of the user device14ofFIG. 1. Further note that the IO device interface module62and/or the memory interface modules may be collectively or individually referred to as IO ports.

FIG. 3is a schematic block diagram of another embodiment of a dispersed storage network (DSN) that includes the distributed storage and task (DST) processing unit16ofFIG. 1, the network24ofFIG. 1, and a set of DST execution (EX) units 1-n. Each DST execution unit includes the DST client module34ofFIG. 1and a memory88. Hereafter, the set of DST execution units may be interchangeably referred to as a set of storage units and the DST execution unit may be interchangeably referred to as a storage unit. Each DST execution unit may be implemented utilizing the DST execution unit36ofFIG. 1. The DSN functions to validate stored encoded data slice integrity.

In various embodiments, a DST execution unit, upon storing a slice, can elect to compute any from among a set of possible integrity check algorithms, possibly computing multiple integrity check values for the same slice. The DST execution unit may not compute all of them at the time the slice is received, but instead may compute the others in the background, as spare computing cycles become available. Each integrity check algorithm can indicate a number of bits of protection (or a probability of a false negative—not detecting an integrity error). Different integrity check algorithms may have different trade-offs in terms of computational efficiency vs. probability of false negatives.

Therefore, at time of read, a DST execution unit can select which integrity check algorithm (from among those that had been pre-computed) to use to verify the slice before returning it. For example, when low on spare computing cycles, the DST execution unit can use a computationally efficient, but more error prone integrity check function, while when there are ample cycles, the DST execution unit can choose to use a more expensive algorithm that is less likely to have a false negative. The integrity check algorithm selection can also be determined by a field in the requesters read request. For example, if response time and latency are the primary concern for the requester, it can indicate to the DST execution unit to bypass the integrity check or to use only the fastest ones, while a requester more concerned with correctness of the data may be willing to wait for a more thorough integrity check function. For further proof against false-negatives, the DST execution unit can randomly/round-robin test different integrity check algorithms, such that a false-positive by one function might be detected by a different algorithm.

In an embodiment, a processing system of a dispersed storage and task (DST) execution unit comprises at least one processor and a memory that stores operational instructions, that when executed by the at least one processor causes the processing system to receive an encoded data slice for storage by the DST execution unit. A plurality of initial integrity values are generated by executing a plurality of integrity check algorithms on the encoded data slice. The encoded data slice and the plurality of initial integrity values are stored in a memory of the DST execution unit. A subset of the plurality of integrity check algorithms are selected in response to a request to retrieve the encoded data slice. At least one final integrity value is generated by executing the subset of the plurality of integrity check algorithms on the encoded data slice stored in memory. An integrity status is generated by comparing the at least one final integrity value to the corresponding subset of the plurality of initial integrity values.

In various embodiments of the processing system, the plurality of integrity check algorithms to be executed on the encoded data slice are selected by the processing system. In some embodiments, the plurality of integrity check algorithms are selected based on at least one of: a processing resource availability level, a desired false-negative probability level, or an algorithm computational efficiency level. In some embodiments, a first integrity check algorithm is more error-prone than a second integrity check algorithm, wherein the plurality of integrity check algorithms selected includes the first integrity check algorithm in response to determining that processing resource availability is low, and where the plurality of integrity check algorithms selected includes the second integrity check algorithm in response to determining that sufficient processing resources are available. In some embodiments, a first integrity check algorithm is faster than a second integrity check algorithm, and the plurality of integrity check algorithms selected includes the first integrity check algorithm in response to determining that a low desired latency level is required.

In various embodiments of the processing system, the operational instructions, when executed by the at least one processor, further cause the processing system to generate a plurality of priority levels corresponding to each of the plurality of integrity check algorithms, where the plurality of integrity check algorithms are executed in an order based on the plurality of priority levels. In some embodiments, the plurality of identifiers corresponding to the plurality of integrity check algorithms are stored in the memory.

In various embodiments of the processing system, the subset of the plurality of integrity check algorithms is a non-null proper subset that is selected based on at least one of: an available resource level, a required retrieval performance level, and a recovery desired maximum false-negative probability level. In some embodiments, the integrity status indicates a favorable comparison when a result of the comparison indicates that the plurality of initial integrity values and the at least one final integrity value are substantially identical, and the integrity status indicates an unfavorable comparison when a result of the comparison indicates that the at least one initial integrity value and the at least one final integrity value are not substantially identical. In some embodiments, the encoded data slice and the integrity status are transmitted to an entity that generated the request to retrieve the encoded data slice.

In an example of operation of the validating of the stored encoded data slice integrity, a storage unit can receive an encoded data slice for storage. For example, the DST execution unit1receives, via the network24, slice 1 of a set of slices 1-n from the DST client module34of the DST processing unit16. Having received the encoded data slice for storage, the storage unit can select one or more integrity check algorithms from a plurality of integrity check algorithms based on one or more of a processing resource availability level, a desired false-negative probability level, an algorithm computational efficiency level, a predetermination, a requested list of algorithms, a desired latency level, system registry information, and/or an integrity approach. For example, the DST client module34of the DST execution unit1can select a more computationally efficient algorithm that is more error-prone when low on processing resource availability. As another example, the DST client module34utilizes a less error-prone algorithm that requires more processing resources when sufficient processing resources are available. As yet another example, the DST client module34utilizes a faster computational algorithm when a low desired latency level is required.

Having selected the integrity check algorithms, the storage unit can perform the selected one or more integrity check algorithms on the received encoded data slice to produce one or more integrity values 1-L. For example, the DST client module34of the DST execution unit1performs a first integrity check algorithm on the received encoded data slice to produce an integrity value 1-1, performs a second integrity check algorithm on the received encoded data slice to produce an integrity value 1-2, through performing an Lth integrity check algorithm on a received encoded data slice to produce an integrity value 1-L. The performing of the selected one or more integrity check algorithms can further include executing a highest priority integrity check algorithm first followed by a next highest priority integrity check algorithm etc.

Having produced the integrity values, the storage unit can facilitate storage of the received encoded data slice and the one or more integrity values in a local memory. For example, the DST client module34of the DST execution unit1stores the encoded data slice in the memory88of the DST execution unit1and stores the integrity values 1-1 through 1-L in the memory88. Facilitating the storage can further include the DST processing unit34storing the identifiers of the integrity check algorithms in the memory88.

When recovering the encoded data slice, the storage unit can retrieve the encoded data slice and at least one integrity value from the local memory. Retrieving the encoded data slice can further include retrieving the identifiers of the integrity check algorithms from the memory88. Having retrieved the encoded data slice, the storage unit can select one or more recovery integrity check algorithms (e.g., a subset of the selected one or more integrity check algorithms) based on the identifiers of the integrity check algorithms corresponding to the one or more integrity values. The selection can be based on one or more of an available resource level, a required retrieval performance level, a recovery desired maximum false-negative probability level, and/or a prioritization of the recovery integrity check algorithms.

Having selected the recovery integrity check algorithms, the storage unit can perform the selected one or more recovery integrity check algorithms on the retrieved encoded data slice to produce one or more calculated integrity values. Having produced the calculated integrity values, the storage unit can indicate the integrity status of the retrieved encoded data slice based on a comparison of the retrieved at least one integrity value and corresponding one or more calculated integrity values. For example, the DST client module34of the DST execution unit1can indicate a favorable comparison when the comparison is substantially the same. As another example, the DST client module34of the DST execution unit1can indicate an unfavorable comparison when the comparison is not substantially the same.

Having indicated the integrity status, the storage unit can send the retrieved encoded data slice and the integrity status to a requesting entity. For example, the DST client module34of the DST execution unit1and sends, via the network24, the retrieved encoded data slice and the integrity status to the DST processing unit16.

FIG. 4is a flowchart illustrating an example of validate stored encoded data slice integrity. In particular, a method is presented for use in conjunction with one or more functions and features described in conjunction withFIGS. 1-4is presented for execution by a dispersed storage and task (DST) execution unit that includes a processor or via another processing system of a dispersed storage network that includes at least one processor and memory that stores instruction that configure the processor or processors to perform the steps described below. Step402includes receiving an encoded data slice for storage by the DST execution unit. Step404includes generating a plurality of initial integrity values by executing a plurality of integrity check algorithms on the encoded data slice. Step406includes storing the encoded data slice and the plurality of initial integrity values in a memory of the DST execution unit. Step408includes selecting a subset of the plurality of integrity check algorithms in response to a request to retrieve the encoded data slice. Step410includes generating at least one final integrity value by executing the subset of the plurality of integrity check algorithms on the encoded data slice stored in memory. Step412includes generating an integrity status by comparing the at least one final integrity value to the corresponding subset of the plurality of initial integrity values.

In various embodiments, the plurality of integrity check algorithms to be executed on the encoded data slice are selected by the processing system. In some embodiments, the plurality of integrity check algorithms are selected based on at least one of: a processing resource availability level, a desired false-negative probability level, or an algorithm computational efficiency level. In some embodiments, a first integrity check algorithm is more error-prone than a second integrity check algorithm, wherein the plurality of integrity check algorithms selected includes the first integrity check algorithm in response to determining that processing resource availability is low, and where the plurality of integrity check algorithms selected includes the second integrity check algorithm in response to determining that sufficient processing resources are available. In some embodiments, a first integrity check algorithm is faster than a second integrity check algorithm, and where the plurality of integrity check algorithms selected includes the first integrity check algorithm in response to determining that a low desired latency level is required.

In various embodiments, the operational instructions, when executed by the at least one processor, further causes the processing system to generate a plurality of priority levels corresponding to each of the plurality of integrity check algorithms, where the plurality of integrity check algorithms are executed in an order based on the plurality of priority levels. In some embodiments, the plurality of identifiers corresponding to the plurality of integrity check algorithms are stored in the memory.

In various embodiments, the subset of the plurality of integrity check algorithms is a non-null proper subset that is selected based on at least one of: an available resource level, a required retrieval performance level, and a recovery desired maximum false-negative probability level. In some embodiments, the integrity status indicates a favorable comparison when a result of the comparison indicates that the plurality of initial integrity values and the at least one final integrity value are substantially identical, and the integrity status indicates an unfavorable comparison when a result of the comparison indicates that the at least one initial integrity value and the at least one final integrity value are not substantially identical. In some embodiments, the encoded data slice and the integrity status are transmitted to an entity that generated the request to retrieve the encoded data slice.

The method described above in conjunction with the computing device and the storage units can alternatively be performed by other modules of the dispersed storage network or by other devices. For example, any combination of a first module, a second module, a third module, a fourth module, etc. of the computing device and the storage units may perform the method described above. In addition, at least one memory section (e.g., a first memory section, a second memory section, a third memory section, a fourth memory section, a fifth memory section, a sixth memory section, etc. of a non-transitory computer readable storage medium) that stores operational instructions can, when executed by one or more processing modules of one or more computing devices and/or by the storage units of the dispersed storage network (DSN), cause the one or more computing devices and/or the storage units to perform any or all of the method steps described above.

The term “module” is used in the description of the various embodiments of the present invention. A module includes a processing module, a functional block, hardware, and/or software stored on memory for performing one or more functions as may be described herein. Note that, if the module is implemented via hardware, the hardware may operate independently and/or in conjunction software and/or firmware. As used herein, a module may contain one or more sub-modules, each of which may be one or more modules.