Abstract:
A distributed storage processing unit encodes data objects into multiple encoded data slices to prevent reconstruction of the original data object using a single encoded data slice, but to allow reconstruction using at least a threshold number of encoded data slices. The distributed storage processing unit can decide to whether and where to cache frequently requested data slices. When retrieving data slices related to a particular data object, a check can be made to determine if the data slices are cached in a temporary memory associated with the distributed storage processing unit, or elsewhere in the distributed storage network. This check can be facilitated by storing data slices and a hash table identifying the location of stored data slices in the same temporary memory.

Description:
CROSS REFERENCE TO RELATED PATENTS 
       [0001]    This patent application is claiming priority under 35 USC §119(e) to a provisionally filed patent application entitled “DISTRIBUTED STORAGE NETWORK DATA ROUTING,” having a provisional filing date of Oct. 30, 2009 and a provisional Ser. No. 61/256,419, filed Oct. 30, 2009, which is incorporated herein in its entirety by reference for all purposes. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    NOT APPLICABLE 
       INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC 
       [0003]    NOT APPLICABLE 
       BACKGROUND OF THE INVENTION 
       [0004]    1. Technical Field of the Invention 
         [0005]    This invention relates generally to computing and more particularly to storage of information. 
         [0006]    2. Description of Related Art 
         [0007]    Computing systems are known to communicate, process, and store data. Such computing systems range from wireless smart phones to data centers that support millions of web searches, stock trades, or on-line purchases every day. Computing processing is known to manipulate data from one form into another. For instance, raw picture data from an image sensor may be compressed, or manipulated, in accordance with a picture compression standard to produce a standardized compressed picture that can be saved or shared with others. Computer processing capability continues to advance as processing speed advances and software applications that perform the manipulation become more sophisticated. 
         [0008]    With the advances in computing processing speed and communication speed, computers manipulate real time media from voice to streaming high definition video. Purpose-built communications devices, like the phone, are being replaced by more general-purpose information appliances. For example, smart phones can support telephony communications but they are also capable of text messaging, and accessing the internet to perform functions including email, web browsing, remote applications access, and media communications. Media communications includes telephony voice, image transfer, music files, video files, real time video streaming and more. 
         [0009]    Each type of computing system is constructed, and hence operates, in accordance with one or more communication, processing, and storage standards. With such standards, and with advances in technology, more and more of the global information content is being converted into electronic formats. For example, more digital cameras are now being sold than film cameras, thus producing more digital pictures. High growth rates exist for web based programming that until recently was all broadcast by just a few over the air television stations and cable television providers. Digital content standards, such as used in pictures, papers, books, video entertainment, home video, all enable this global transformation to a digital format. Electronic content pervasiveness is producing increasing demands on the storage function of computing systems. 
         [0010]    A typical computer storage function includes one or more memory devices to match the needs of the various operational aspects of the processing and communication functions. For example, a memory device may include solid-state NAND flash, random access memory (RAM), read only memory (ROM), a mechanical hard disk drive. Each type of memory device has a particular performance range and normalized cost. The computing system architecture optimizes the use of one or more types of memory devices to achieve the desired functional and performance goals of the computing system. Generally, the immediacy of access dictates what type of memory device is used. For example, RAM memory can be accessed in any random order with a constant response time. By contrast, memory device technologies that require physical movement such as magnetic discs, tapes, and optical discs, have a variable responses time as the physical movement can take longer than the data transfer. 
         [0011]    Each type of computer storage system is constructed, and hence operates, in accordance with one or more storage standards. For instance, computer storage systems may operate in accordance with one or more standards including, but not limited to network file system (NFS), flash file system (FFS), disk file system (DFS), small computer system interface (SCSI), internet small computer system interface (iSCSI), file transfer protocol (FTP), and web-based distributed authoring and versioning (WebDAV). An operating systems (OS) and storage standard may specify the data storage format and interface between the processing subsystem and the memory devices. The interface may specify a structure such as directories and files. Typically a memory controller provides an interface function between the processing function and memory devices. As new storage systems are developed, the memory controller functional requirements may change to adapt to new standards. 
         [0012]    Memory devices may fail, especially those that utilize technologies that require physical movement like a disc drive. For example, it is not uncommon for a disc drive to suffer from bit level corruption on a regular basis, or complete drive failure after an average of three years of use. One common solution is to utilize more costly disc drives that have higher quality internal components. Another solution is to utilize multiple levels of redundant disc drives to abate these issues by replicating the data into two or more copies. One such redundant drive approach is called redundant array of independent discs (RAID). Multiple physical discs comprise an array where parity data is added to the original data before storing across the array. The parity is calculated such that the failure of one or more discs will not result in the loss of the original data. The original data can be reconstructed from the other discs. RAID 5 uses three or more discs to protect data from the failure of any one disc. The parity and redundancy overhead reduces the capacity of what three independent discs can store by one third (n−1=3−2=2 discs of capacity using 3 discs). RAID 6 can recover from a loss of two discs and requires a minimum of four discs with an efficiency of n−2. Typical RAID systems utilize a RAID control to encode and decode the data across the array. 
         [0013]    Drawbacks of the RAID approach include effectiveness, efficiency and security. As more discs are added, the probability of one or two discs failing rises and is not negligible, especially if more desired less costly discs are used. When one disc fails, it should be immediately replaced and the data reconstructed before a second drive fails. To provide high reliability over a long time period, and if the RAID array is part of a national level computing system with occasional site outages, it is also common to mirror RAID arrays at different physical locations. Unauthorized file access becomes a more acute problem when whole copies of the same file are replicated, either on just one storage system site or at two or more sites. In light of the effectiveness, the efficiency of dedicating  1  to  2  discs per array for the RAID overhead is an issue. 
         [0014]    Therefore, a need exists to provide a data storage solution that provides more effective timeless continuity of data, minimizes adverse affects of multiple memory elements failures, provides improved security, can be adapted to a wide variety storage system standards and is compatible with computing and communications systems. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
         [0015]      FIG. 1  is a schematic block diagram of an embodiment of a computing system in accordance with the invention; 
           [0016]      FIG. 2  is a schematic block diagram of an embodiment of a computing core in accordance with the invention; 
           [0017]      FIG. 3  is a schematic block diagram of an embodiment of a distributed storage processing unit in accordance with the invention; 
           [0018]      FIG. 4  is a schematic block diagram of an embodiment of a grid module in accordance with the invention; 
           [0019]      FIG. 5  is a diagram of an example embodiment of error coded data slice creation in accordance with the invention; 
           [0020]      FIG. 6  is a schematic block diagram of another embodiment of a computing system in accordance with the invention; 
           [0021]      FIG. 7  is a flowchart illustrating the retrieval of distributedly stored data; 
           [0022]      FIG. 8  is a schematic block diagram of another embodiment of a computing system in accordance with the invention; 
           [0023]      FIG. 9  is a schematic block diagram of an embodiment of a distributed storage (DS) unit in accordance with the invention; 
           [0024]      FIG. 10  is a flowchart illustrating the storing of distributedly stored data; 
           [0025]      FIG. 11  is a schematic block diagram of another embodiment of a computing system in accordance with the invention; 
           [0026]      FIG. 12  is a block diagram of an embodiment of layered message creation in accordance with the invention; 
           [0027]      FIG. 13  is a flowchart illustrating the creation of a layered message; and 
           [0028]      FIG. 14  is a flowchart illustrating the processing of a layered message. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0029]      FIG. 1  is a schematic block diagram of a computing system  10  that includes one or more of a first type of user devices  12 , one or more of a second type of user devices  14 , at least one distributed storage (DS) processing unit  16 , at least one DS managing unit  18 , at least one storage integrity processing unit  20 , and a distributed storage network (DSN) memory  22  coupled via a network  24 . The network  24  may include one or more wireless and/or wire lined communication systems; one or more private intranet systems and/or public internet systems; and/or one or more local area networks (LAN) and/or wide area networks (WAN). 
         [0030]    The DSN memory  22  includes a plurality of distributed storage (DS) units  36  for storing data of the system. Each of the DS units  36  includes a processing module and memory and may be located at a geographically different site than the other DS units (e.g., one in Chicago, one in Milwaukee, etc.). The processing module may be a single processing device or a plurality of processing devices. Such a processing device may be a microprocessor, micro-controller, digital signal processor, microcomputer, central processing unit, field programmable gate array, programmable logic device, state machine, logic circuitry, analog circuitry, digital circuitry, and/or any device that manipulates signals (analog and/or digital) based on hard coding of the circuitry and/or operational instructions. The processing module may have an associated memory and/or memory element, which may be a single memory device, a plurality of memory devices, and/or embedded circuitry of the processing module. Such a memory device may be a read-only memory, random access memory, volatile memory, non-volatile memory, static memory, dynamic memory, flash memory, cache memory, and/or any device that stores digital information. Note that if the processing module includes more than one processing device, the processing devices may be centrally located (e.g., directly coupled together via a wired and/or wireless bus structure) or may be distributedly located (e.g., cloud computing via indirect coupling via a local area network and/or a wide area network). Further note that when the processing module implements one or more of its functions via a state machine, analog circuitry, digital circuitry, and/or logic circuitry, the memory and/or memory element storing the corresponding operational instructions may be embedded within, or external to, the circuitry comprising the state machine, analog circuitry, digital circuitry, and/or logic circuitry. Still further note that, the memory element stores, and the processing module executes, hard coded and/or operational instructions corresponding to at least some of the steps and/or functions illustrated in  FIGS. 1-14 . 
         [0031]    Each of the user devices  12 - 14 , the DS processing unit  16 , the DS managing unit  18 , and the storage integrity processing unit  20  may be a portable computing device (e.g., a social networking device, a gaming device, a cell phone, a smart phone, a personal digital assistant, a digital music player, a digital video player, a laptop computer, a handheld computer, a video game controller, and/or any other portable device that includes a computing core) and/or a fixed computing device (e.g., a personal computer, 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). Such a portable or fixed computing device includes a computing core  26  and one or more interfaces  30 ,  32 , and/or  33 . An embodiment of the computing core  26  will be described with reference to  FIG. 2 . 
         [0032]    With respect to the interfaces, each of the interfaces  30 ,  32 , and  33  includes software and/or hardware to support one or more communication links via the network  24  and/or directly. For example, interfaces  30  support a communication link (wired, wireless, direct, via a LAN, via the network  24 , etc.) between the first type of user device  14  and the DS processing unit  16 . As another example, DSN interface  32  supports a plurality of communication links via the network  24  between the DSN memory  22  and the DS processing unit  16 , the first type of user device  12 , and/or the storage integrity processing unit  20 . As yet another example, interface  33  supports a communication link between the DS managing unit  18  and any one of the other devices and/or units  12 ,  14 ,  16 ,  20 , and/or  22  via the network  24 . 
         [0033]    In general and with respect to data storage, the system  10  supports three primary functions: distributed network data storage management, distributed data storage and retrieval, and data storage integrity verification. In accordance with these three primary functions, data can be distributedly stored in a plurality of physically different locations and subsequently retrieved in a reliable and secure manner regardless of failures of individual storage devices, failures of network equipment, the duration of storage, the amount of data being stored, attempts at hacking the data, etc. 
         [0034]    The DS managing unit  18  performs distributed network data storage management functions, which include establishing distributed data storage parameters, performing network operations, performing network administration, and/or performing network maintenance. The DS managing unit  18  establishes the distributed data storage parameters (e.g., allocation of virtual DSN memory space, distributed storage parameters, security parameters, billing information, user profile information, etc.) for one or more of the user devices  12 - 14  (e.g., established for individual devices, established for a user group of devices, established for public access by the user devices, etc.). For example, the DS managing unit  18  coordinates the creation of a vault (e.g., a virtual memory block) within the DSN memory  22  for a user device (for a group of devices, or for public access). The DS managing unit  18  also determines the distributed data storage parameters for the vault. In particular, the DS managing unit  18  determines a number of slices (e.g., the number that a data segment of a data file and/or data block is partitioned into for distributed storage) and a read threshold value (e.g., the minimum number of slices required to reconstruct the data segment). 
         [0035]    As another example, the DS managing module  18  creates and stores, locally or within the DSN memory  22 , user profile information. The user profile information includes one or more of authentication information, permissions, and/or the security parameters. The security parameters may include one or more of encryption/decryption scheme, one or more encryption keys, key generation scheme, and data encoding/decoding scheme. 
         [0036]    As yet another example, the DS managing unit  18  creates billing information for a particular user, user group, vault access, public vault access, etc. For instance, the DS managing unit  18  tracks the number of times user accesses a private vault and/or public vaults, which can be used to generate a per-access bill. In another instance, the DS managing unit  18  tracks the amount of data stored and/or retrieved by a user device and/or a user group, which can be used to generate a per-data-amount bill. 
         [0037]    The DS managing unit  18  also performs network operations, network administration, and/or network maintenance. As at least part of performing the network operations and/or administration, the DS managing unit  18  monitors performance of the devices and/or units of the system  10  for potential failures, determines the devices and/or unit&#39;s activation status, determines the devices&#39; and/or units&#39; loading, and any other system level operation that affects the performance level of the system  10 . For example, the DS managing unit  18  receives and aggregates network management alarms, alerts, errors, status information, performance information, and messages from the devices  12 - 14  and/or the units  16 ,  20 ,  22 . For example, the DS managing unit  18  receives a simple network management protocol (SNMP) message regarding the status of the DS processing unit  16 . 
         [0038]    The DS managing unit  18  performs the network maintenance by identifying equipment within the system  10  that needs replacing, upgrading, repairing, and/or expanding. For example, the DS managing unit  18  determines that the DSN memory  22  needs more DS units  36  or that one or more of the DS units  36  needs updating. 
         [0039]    The second primary function (i.e., distributed data storage and retrieval) begins and ends with a user device  12 - 14 . For instance, if a second type of user device  14  has a data file  38  and/or data block  40  to store in the DSN memory  22 , it send the data file  38  and/or data block  40  to the DS processing unit  16  via its interface  30 . As will be described in greater detail with reference to  FIG. 2 , the interface  30  functions 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 interface  30  may attach a user identification code (ID) to the data file  38  and/or data block  40 . 
         [0040]    The DS processing unit  16  receives the data file  38  and/or data block  40  via its interface  30  and performs a distributed storage (DS) process  34  thereon (e.g., an error coding dispersal storage function). The DS processing  34  begins by partitioning the data file  38  and/or data block  40  into one or more data segments, which is represented as Y data segments. For example, the DS processing  34  may partition the data file  38  and/or data block  40  into a fixed byte size segment (e.g., 2 1  to 2 n  bytes, where n=&gt;2) or a variable byte size (e.g., change byte size from segment to segment, or from groups of segments to groups of segments, etc.). 
         [0041]    For each of the Y data segments, the DS processing  34  error encodes (e.g., forward error correction (FEC), information dispersal algorithm, or error correction coding) and slices (or slices then error encodes) the data segment into a plurality of error coded (EC) data slices  42 - 48 , which is represented as X slices per data segment. The number of slices (X) per segment, which corresponds to a number of pillars n, is set in accordance with the distributed data storage parameters and the error coding scheme. For example, if a Reed-Solomon (or other FEC scheme) is used in an n/k system, then a data segment is divided into n slices, where k number of slices is needed to reconstruct the original data (i.e., k is the threshold). As a few specific examples, the n/k factor may be 5/3; 6/4; 8/6; 8/5; 16/10. 
         [0042]    For each slice  42 - 48 , the DS processing unit  16  creates a unique slice name and appends it to the corresponding slice  42 - 48 . The slice name includes universal DSN memory addressing routing information (e.g., virtual memory addresses in the DSN memory  22 ) and user-specific information (e.g., user ID, file name, data block identifier, etc.). 
         [0043]    The DS processing unit  16  transmits the plurality of EC slices  42 - 48  to a plurality of DS units  36  of the DSN memory  22  via the DSN interface  32  and the network  24 . The DSN interface  32  formats each of the slices for transmission via the network  24 . For example, the DSN interface  32  may utilize an internet protocol (e.g., TCP/IP, etc.) to packetize the slices  42 - 48  for transmission via the network  24 . 
         [0044]    The number of DS units  36  receiving the slices  42 - 48  is dependent on the distributed data storage parameters established by the DS managing unit  18 . For example, the DS managing unit  18  may indicate that each slice is to be stored in a different DS unit  36 . As another example, the DS managing unit  18  may indicate that like slice numbers of different data segments are to be stored in the same DS unit  36 . For example, the first slice of each of the data segments is to be stored in a first DS unit  36 , the second slice of each of the data segments is to be stored in a second DS unit  36 , etc. In this manner, the data is encoded and distributedly stored at physically diverse locations to improved data storage integrity and security. Further examples of encoding the data segments will be provided with reference to one or more of  FIGS. 2-9 . 
         [0045]    Each DS unit  36  that receives a slice  42 - 48  for storage translates the virtual DSN memory address of the slice into a local physical address for storage. Accordingly, each DS unit  36  maintains a virtual to physical memory mapping to assist in the storage and retrieval of data. 
         [0046]    The first type of user device  12  performs a similar function to store data in the DSN memory  22  with the exception that it includes the DS processing. As such, the device  12  encodes and slices the data file and/or data block it has to store. The device then transmits the slices  35  to the DSN memory via its DSN interface  32  and the network  24 . 
         [0047]    For a second type of user device  14  to retrieve a data file or data block from memory, it issues a read command via its interface  30  to the DS processing unit  16 . The DS processing unit  16  performs the DS processing  34  to identify the DS units  36  storing the slices of the data file and/or data block based on the read command. The DS processing unit  16  may also communicate with the DS managing unit  18  to verify that the user device  14  is authorized to access the requested data. 
         [0048]    Assuming that the user device is authorized to access the requested data, the DS processing unit  16  issues slice read commands to at least a threshold number of the DS units  36  storing the requested data (e.g., to at least IO DS units for a 16/10 error coding scheme). Each of the DS units  36  receiving the slice read command, verifies the command, accesses its virtual to physical memory mapping, retrieves the requested slice, or slices, and transmits it to the DS processing unit  16 . 
         [0049]    Once the DS processing unit  16  has received a read threshold number of slices for a data segment, it performs an error decoding function and de-slicing to reconstruct the data segment. When Y number of data segments has been reconstructed, the DS processing unit  16  provides the data file  38  and/or data block  40  to the user device  14 . Note that the first type of user device  12  performs a similar process to retrieve a data file and/or data block. 
         [0050]    The storage integrity processing unit  20  performs the third primary function of data storage integrity verification. In general, the storage integrity processing unit  20  periodically retrieves slices  45 , and/or slice names, of a data file or data block of a user device to verify that one or more slices have not been corrupted or lost (e.g., the DS unit failed). The retrieval process mimics the read process previously described. 
         [0051]    If the storage integrity processing unit  20  determines that one or more slices is corrupted or lost, it rebuilds the corrupted or lost slice(s) in accordance with the error coding scheme. The storage integrity processing unit  20  stores the rebuild slice, or slices, in the appropriate DS unit(s)  36  in a manner that mimics the write process previously described. 
         [0052]      FIG. 2  is a schematic block diagram of an embodiment of a computing core  26  that includes a processing module  50 , a memory controller  52 , main memory  54 , a video graphics processing unit  55 , an input/output ( 10 ) controller  56 , a peripheral component interconnect (PCI) interface  58 , at least one IO device interface module  62 , a read only memory (ROM) basic input output system (BIOS)  64 , and one or more memory interface modules. The memory interface module(s) includes one or more of a universal serial bus (USB) interface module  66 , a host bus adapter (HBA) interface module  68 , a network interface module  70 , a flash interface module  72 , a hard drive interface module  74 , and a DSN interface module  76 . 
         [0053]    Note the DSN interface module  76  and/or the network interface module  70  may function as the interface  30  of the user device  14  of  FIG. 1 . Further note that the IO device interface module  62  and/or the memory interface modules may be collectively or individually referred to as IO ports. 
         [0054]    The processing module  50  may be a single processing device or a plurality of processing devices. Such a processing device may be a microprocessor, micro-controller, digital signal processor, microcomputer, central processing unit, field programmable gate array, programmable logic device, state machine, logic circuitry, analog circuitry, digital circuitry, and/or any device that manipulates signals (analog and/or digital) based on hard coding of the circuitry and/or operational instructions. The processing module  50  may have an associated memory and/or memory element, which may be a single memory device, a plurality of memory devices, and/or embedded circuitry of the processing module  50 . Such a memory device may be a read-only memory, random access memory, volatile memory, non-volatile memory, static memory, dynamic memory, flash memory, cache memory, and/or any device that stores digital information. Note that if the processing module  50  includes more than one processing device, the processing devices may be centrally located (e.g., directly coupled together via a wired and/or wireless bus structure) or may be distributedly located (e.g., cloud computing via indirect coupling via a local area network and/or a wide area network). Further note that when the processing module  50  implements one or more of its functions via a state machine, analog circuitry, digital circuitry, and/or logic circuitry, the memory and/or memory element storing the corresponding operational instructions may be embedded within, or external to, the circuitry comprising the state machine, analog circuitry, digital circuitry, and/or logic circuitry. Still further note that, the memory element stores, and the processing module  50  executes, hard coded and/or operational instructions corresponding to at least some of the steps and/or functions illustrated in  FIGS. 1-14 . 
         [0055]      FIG. 3  is a schematic block diagram of an embodiment of a dispersed storage (DS) processing module  34  of user device  12  and/or of the DS processing unit  16 . The DS processing module  34  includes a gateway module  78 , an access module  80 , a grid module  82 , and a storage module  84 . The DS processing module  34  may also include an interface  30  and the DSnet interface  32  or the interfaces  68  and/or  70  may be part of user  12  or of the DS processing unit  14 . The DS processing module  34  may further include a bypass/feedback path between the storage module  84  to the gateway module  78 . 
         [0056]    In an example of storing data, the gateway module  78  receives an incoming data object (e.g., a data file, a data block, an EC data slice, etc.) that includes a user ID field  86 , an object name field  88 , and the data field  40 . The gateway module  78  authenticates the user associated with the data object by verifying the user ID  86  with the managing unit  18  and/or another authenticating unit. When the user is authenticated, the gateway module  78  obtains user information from the management unit  18 , the user device, and/or the other authenticating unit. The user information includes a vault identifier, operational parameters, and user attributes (e.g., user data, billing information, etc.). A vault identifier identifies a vault, which is a virtual memory space that maps to a set of DS storage units  36 . For example, vault  1  (i.e., user  1 &#39;s DSN memory space) includes eight DS storage units (X=8 wide) and vault  2  (i.e., user  2 &#39;s DSN memory space) includes sixteen DS storage units (X=16 wide). The operational parameters may include an error coding algorithm, the width n (number of pillars X or slices per segment for this vault), a read threshold T, an encryption algorithm, a slicing parameter, a compression algorithm, an integrity check method, caching settings, parallelism settings, and/or other parameters that may be used to access the DSN memory layer. 
         [0057]    The gateway module uses the user information to assign a source name to the data. 
         [0058]    For instance, the gateway module  60  determines the source name of the data object  40  based on the vault identifier and the data object. For example, the source name may contain a data name (block number or a file number), the vault generation number, the reserved field, and the vault identifier. The data name may be randomly assigned but is associated with the user data object. 
         [0059]    The access module  62  receives the data object  40  and creates a series of data segments  1  through Y  90 - 92  therefrom. The number of segments Y may be chosen or randomly assigned based on a selected segment size and the size of the data object. For example, if the number of segments is chosen to be a fixed number, then the size of the segments varies as a function of the size of the data object. For instance, if the data object is an image file of 4,194,304 eight bit bytes (e.g., 33,554,432 bits) and the number of segments Y=131,072, then each segment is 256 bits or 32 bytes. As another example, if segment sized is fixed, then the number of segments Y varies based on the size of data object. For instance, if the data object is an image file of 4,194,304 bytes and the fixed size of each segment is 4,096 bytes, the then number of segments Y=1,024. Note that each segment is associated with the source name. 
         [0060]    The grid module  82  may pre-manipulate (e.g., compression, encryption, cyclic redundancy check (CRC), etc.) each of the data segments before performing an error coding function of the error coding dispersal storage function to produce a pre-manipulated data segment. The grid module  82  then error encodes (e.g., Reed-Solomon, Convolution encoding, Trellis encoding, etc.) the data segment or pre-manipulated data segment into X error coded data slices  42 - 44 . The grid module  64  determines a unique slice name for each error coded data slice and attaches it to the data slice. 
         [0061]    In some embodiments, the slice name includes a universal routing information field and a vault specific field. In an embodiment, the universal routing information field is 24 bytes and the vault specific field is 24 bytes. The universal routing information field contains a slice index, the vault ID, the vault generation, and the reserved field. The slice index is based on the pillar number n and the vault ID such that it is unique for each pillar (e.g., slices of the same pillar for the same vault for any segment will share the same slice index). The vault specific field contains a data name that may include the file ID and a segment number (e.g., a sequential numbering of the data segments of a simple data object or a data block number). 
         [0062]    The data name field may be the same for slice names of slices for the same data segment and may vary for slice names of different data segments. The file ID portion of data name may not vary for any slice name of the same data object. Note that the DS processing module  34  may modify the data name field such that the file ID is not transparent (e.g., produce a data name from a hash of the source name to disguise the file ID). 
         [0063]    The value X, or the number of pillars (e.g., X=16), is chosen as a parameter of the error coding dispersal storage function. Other parameters of the error coding dispersal function include a read threshold T, a write threshold W, etc. The read threshold (e.g., T=10, when X=16) corresponds to the minimum number of error-free error coded data slices required to reconstruct the data segment. In other words, the DS processing module  34  can compensate for X-T (e.g., 16−10=6) missing error coded data slices per data segment. The write threshold W corresponds to a minimum number of DS storage units that acknowledge proper storage of their respective data slices before the DS processing module indicates proper storage of the encoded data segment. Note that the write threshold is greater than or equal to the read threshold for a given number of pillars (X). 
         [0064]    The grid module  82  also determines which of the DS storage units  36  will store the EC data slices based on a dispersed storage memory mapping associated with the user&#39;s vault and/or DS storage unit  36  attributes. The DS storage unit attributes includes availability, self-selection, performance history, link speed, link latency, ownership, available DSN memory, domain, cost, a prioritization scheme, a centralized selection message from another source, a lookup table, data ownership, and/or any other factor to optimize the operation of the computing system. Note that the number of DS storage units  36  is equal to or greater than the number of pillars (e.g., X) so that no more than one error coded data slice of the same data segment is stored on the same DS storage unit  36 . Further note that EC data slices of the same pillar number but of different segments (e.g., EC data slice  1  of data segment  1  and EC data slice  1  of data segment  2 ) may be stored on the same or different DS storage units  36 . 
         [0065]    The storage module  84  performs an integrity check on the EC data slices and, when successful, transmits the EC data slices  1  through X of each segment  1  through Y to the DS Storage units. Each of the DS storage units  36  stores its EC data slice and keeps a table to convert the virtual DSN address of the EC data slice into physical storage addresses. 
         [0066]    In an example of a read operation, the user device  12  and/or  14  sends a read request to the DS processing unit  14 , which authenticates the request. When the request is authentic, the DS processing unit  14  sends a read message to each of the DS storage units  36  storing slices of the data object being read. The slices are received via the DSnet interface  32  and processed by the storage module  84 , which performs a parity check and provides the slices to the grid module  82  when the parity check was successful. The grid module  82  decodes the slices in accordance with the error coding dispersal storage function to reconstruct the data segment. The access module  80  reconstructs the data object from the data segments and the gateway module  78  formats the data object for transmission to the user device. 
         [0067]      FIG. 4  is a schematic block diagram of an embodiment of a grid module  82  that includes a control unit  73 , a pre-data manipulator  75 , an encoder  77 , a slicer  79 , a post-data manipulator  81 , a pre-data de-manipulator  83 , a decoder  85 , a de-slicer  87 , and/or a post-data de-manipulator  89 . Note that the control unit  73  may be partially or completely external to the grid module  82 . For example, the control unit  73  may be part of the computing core at a remote location, part of a user device, part of the DS managing unit  18 , or distributed amongst one or more DS storage units. 
         [0068]    In an example of write operation, the pre-data manipulator  75  receives a data segment  90 - 92  and a write instruction from an authorized user device. The pre-data manipulator  75  determines if pre-manipulation of the data segment  90 - 92  is required and, if so, what type. The pre-data manipulator  75  may make the determination independently or based on instructions from the control unit  73 , where the determination is based a computing system-wide predetermination, a table lookup, vault parameters associated with the user identification, the type of data, security requirements, available DSN memory, performance requirements, and/or other metadata. 
         [0069]    Once a positive determination is made, the pre-data manipulator  75  manipulates the data segment  90 - 92  in accordance with the type of manipulation. For example, the type of manipulation may be compression (e.g., Lempel-Ziv-Welch, Huffman, Golomb, fractal, wavelet, etc.), signatures (e.g., Digital Signature Algorithm (DSA), Elliptic Curve DSA, Secure Hash Algorithm, etc.), watermarking, tagging, encryption (e.g., Data Encryption Standard, Advanced Encryption Standard, etc.), adding metadata (e.g., time/date stamping, user information, file type, etc.), cyclic redundancy check (e.g., CRC32), and/or other data manipulations to produce the pre-manipulated data segment. 
         [0070]    The encoder  77  encodes the pre-manipulated data segment  92  using a forward error correction (FEC) encoder (and/or other type of erasure coding and/or error coding) to produce an encoded data segment  94 . The encoder  77  determines which forward error correction algorithm to use based on a predetermination associated with the user&#39;s vault, a time based algorithm, user direction, DS managing unit direction, control unit direction, as a function of the data type, as a function of the data segment  92  metadata, and/or any other factor to determine algorithm type. The forward error correction algorithm may be Golay, Multidimensional parity, Reed-Solomon, Hamming, Bose Ray Chauduri Hocquenghem (BCH), Cauchy-Reed-Solomon, or any other FEC encoder. Note that the encoder  77  may use a different encoding algorithm for each data segment  92 , the same encoding algorithm for the data segments  92  of a data object, or a combination thereof. 
         [0071]    The encoded data segment  94  is of greater size than the data segment  92  by the overhead rate of the encoding algorithm by a factor of d*(X/T), where d is size of the data segment  92 , X is the width or number of slices, and T is the read threshold. In this regard, the corresponding decoding process can accommodate at most X-T missing EC data slices and still recreate the data segment  92 . For example, if X=16 and T=10, then the data segment  92  will be recoverable as long as 10 or more EC data slices per segment are not corrupted. 
         [0072]    The slicer  79  transforms the encoded data segment  94  into EC data slices in accordance with the slicing parameter from the vault for this user and/or data segment  92 . For example, if the slicing parameter is X=16, then the slicer slices each encoded data segment  94  into 16 encoded slices. 
         [0073]    The post-data manipulator  81  performs, if enabled, post-manipulation on the encoded slices to produce the EC data slices. If enabled, the post-data manipulator  81  determines the type of post-manipulation, which may be based on a computing system-wide predetermination, parameters in the vault for this user, a table lookup, the user identification, the type of data, security requirements, available DSN memory, performance requirements, control unit directed, and/or other metadata. Note that the type of post-data manipulation may include slice level compression, signatures, encryption, CRC, addressing, watermarking, tagging, adding metadata, and/or other manipulation to improve the effectiveness of the computing system. 
         [0074]    In an example of a read operation, the post-data de-manipulator  89  receives at least a read threshold number of EC data slices and performs the inverse function of the post-data manipulator  81  to produce a plurality of encoded slices. The de-slicer  87  de-slices the encoded slices to produce an encoded data segment  94 . The decoder  85  performs the inverse function of the encoder  77  to recapture the data segment  90 - 92 . The pre-data de-manipulator  83  performs the inverse function of the pre-data manipulator  75  to recapture the data segment. 
         [0075]      FIG. 5  is a diagram of an example of slicing an encoded data segment  94  by the slicer  79 . In this example, the encoded data segment includes thirty-two bits, but may include more or less bits. The slicer  79  disperses the bits of the encoded data segment  94  across the EC data slices in a pattern as shown. As such, each EC data slice does not include consecutive bits of the data segment  94  reducing the impact of consecutive bit failures on data recovery. For example, if EC data slice  2  (which includes bits  1 ,  5 ,  9 ,  13 ,  17 ,  25 , and  29 ) is unavailable (e.g., lost, inaccessible, or corrupted), the data segment can be reconstructed from the other EC data slices (e.g.,  1 ,  3  and  4  for a read threshold of 3 and a width of 4). 
         [0076]      FIG. 6  is a schematic block diagram of another embodiment of a computing system  102  that may provide access to slices from a cache memory in addition to a DSN memory. The computing system  102  includes a plurality of user devices  1 -U, a DS processing unit  16 , a cache memory  103 , and the DSN memory  22 . 
         [0077]    One of the user devices  1 -U may from time to time request retrieval of a data object by sending a retrieval request message to the DS processing unit  16 . The DS processing unit  16  determines where to retrieve the slices to reconstruct the data object. The slices may be located in the cache memory  103 . The DS processing unit  16  may have previously stored the slices in the cache memory  103 . In another embodiment, at least two DS processing units may communicate with each other to locate and retrieve slices stored in cache memory  103 . Note that more than one cache memory may be utilized in the system. 
         [0078]    The cache memory  103  includes a slice memory  104  and a distributed hash table (DHT)  106 , and may be implemented with one or more of a magnetic hard disk, NAND flash, read only memory, optical disk, and/or any other type of read-only, or read/write memory. In an embodiment, the cache memory  103  may be implemented as part of the DS processing unit. 
         [0079]    The slice memory  104  stores EC data slices received as slices from the DS processing unit  16 . The slice memory sends the slices to the DS processing unit  16  upon retrieval. Note that the speed of slice retrieval may be faster retrieving slices from the slice memory  104  as compared to retrieving the same slices from the DSN memory. 
         [0080]    The DHT  106  lists slice name locations for slices stored in the slice memory. In another embodiment, the DHT  106  lists slice name locations for slices stored in at least one other cache memory. 
         [0081]    In an example of operation, the DS processing unit  16  tracks the frequency of retrievals of the same data object from the DSN memory  22 . The DS processing unit stores the retrieved slices in the cache memory  103  and updates the DHT  106  when the frequency of retrievals reaches a threshold. The DS processing unit  16  queries the DHT  106  to determine if the slices are stored in the cache memory  103  when receiving a retrieval request from a user device  1 -U. The DS processing unit  16  retrieves the slices, reconstructs the data object, and sends the data object to the requesting user device when the DHT query indicates that the slices are stored in the cache memory. 
         [0082]    In another example of operation, the DS processing unit  16  deletes slices from the cache memory when the DS processing unit  16  determines that the frequency of retrievals for the slices has fallen below a threshold. 
         [0083]    The method to determine when to store slices to the cache memory  103  will be discussed in greater detail with reference to  FIG. 7 . 
         [0084]      FIG. 7  is a flowchart illustrating the retrieval of distributedly stored data where the DS processing unit determines if slices are stored in cache memory before retrieving the slices. 
         [0085]    The method  700  begins with block  701 , where the DS processing unit receives a data object retrieval request from a requester (e.g., a user device or other system element). The request may include the data object name and a retrieve request message. As illustrated by block  703 , the DS processing unit updates access tracking by saving a record of the retrieval with a timestamp in the user vault or other storage area. The DS processing unit may determine the frequency of previous retrievals by averaging the time between the saved time stamps. 
         [0086]    As illustrated by blocks  705  and  707 , the DS processing unit determines if the slices corresponding to the data object retrieval request are in the cache memory by accessing the DHT and searching for the slice names. Note that DS processing unit can determine the slice names based on the data object name as discussed previously. 
         [0087]    As illustrated by block  709 , the DS processing unit retrieves the slices from the cache memory when the DS processing unit determines that the slices corresponding to the data object retrieval request are in the cache memory. The DS processing unit may verify the integrity of the slices before decoding the slices by comparing previously stored checksums to stored checksums. As shown by block  711 , the DS processing unit de-slices and decodes the slices to produce the data object in accordance with the operational parameters as previously discussed. The DS processing unit sends the data object to the requester, as illustrated by block  713 . 
         [0088]    As illustrated by block  715 , the DS processing unit retrieves the slices from the DSN memory when the DS processing unit determines that the slices corresponding to the data object retrieval request are not in the cache memory. The DS processing unit may verify the integrity of the slices before decoding the slices by comparing previously stored checksums to stored checksums. As illustrated by block  717 , the DS processing unit de-slices and decodes the slices to produce the data object in accordance with the operational parameters as previously discussed. 
         [0089]    As illustrated by blocks  719  and  721 , the DS processing unit determines whether to store the slices in the cache memory based on one or more of a comparison of the access tracking to a threshold (e.g., the retrieval frequency is greater than the threshold), a security level, a priority level, a predetermination, and/or a network loading level. As illustrated by block  723 , the DS processing unit sends the data object to the requester when the DS processing unit determines not to store the slices in the cache memory. 
         [0090]    As illustrated by block  725 , the DS processing unit stores the slices in the cache memory and updates the DHT, as illustrated by block  727 , with the slice names and cache memory location when the DS processing unit determines to store the slices in the cache memory. As illustrated by block  729 , the DS processing unit sends the data object to the requester. 
         [0091]    Note that the DS processing unit may determine whether to delete slices in the cache memory based on one or more of a comparison of the access tracking to a threshold (e.g., the retrieval frequency is less than the threshold), the security level, the priority level, the predetermination, and/or the network loading level. The DS processing unit deletes the slices from the cache memory and removes the slice names from the DHT when the DS processing unit determines to delete slices in the cache memory. 
         [0092]      FIG. 8  is a schematic block diagram  800  of another embodiment of a computing system where two or more DS unit storage sets are utilized to concurrently store and retrieve EC data slices in parallel for the same data object. As used herein the term concurrently and parallel can be considered interchangeable unless otherwise specified, and refer generally to the concept of beginning storage or retrieval of one EC data slice before a previous data slice has finished being stored retrieved. 
         [0093]    The computing system includes a DS processing unit  16 , a storage set A, and a storage set B. The DS processing unit  16  stores and retrieves EC data slices to/from the storage sets A and B. Note that two or more storage sets may be utilized. A storage set includes DS units that comprise the pillars for one or more vaults. For example, in a 4/3 vault, DS units  1 - 4  comprise the storage set A. The corresponding second of the two or more storage sets includes DS units  5 - 8  in storage set B. Both storage sets may be utilized to store slices for the same vault. Note that the two or more storage sets may be in the same or different DSN memories. 
         [0094]    In another embodiment of a 16/10 DSN system, storage set A includes DS units  1 - 16  and storage set B includes DS units  17 - 32 . In yet another embodiment, the number of DS units in the storage sets A and B are different. For example, storage set A includes DS units  1 - 16  for a 16/10 approach and storage set B includes DS units  17 - 20  for a 4/3 approach. 
         [0095]    The DS processing unit  16  may determine how to implement parallelism based on a data type, a priority level, a security level, a request, a command, a predetermination, a desired performance level, a system loading indicator, and/or a system configuration. For example, the DS processing unit  16  may utilize two storage sets when the DS processing unit determines that two storage sets will meet the desired level of performance (e.g., retrieval times). 
         [0096]    To implement parallelism, the DS processing unit  16  may operate in one of several embodiments. In a first embodiment, the DS processing unit  16  creates slices for each pillar of a data segment and sends the slices for storage to storage set A substantially in parallel, or concurrently, with creating slices for each pillar of the next data segment and sending the slices for storage to storage set B. In other words, with two storage sets the DS processing unit  16  sends slices for odd data segment numbers to storage set A while in parallel sending slices for even data segment numbers to storage set B. The DS processing unit  16  subsequently retrieves the data object by retrieving slices for each pillar of a data segment from storage set A substantially in parallel with retrieving slices for each pillar of the next data segment from storage set B. 
         [0097]    In a second embodiment, the DS processing unit  16  creates slices for each pillar of a series of data segments  1  through X and sends the slices for storage to storage set A substantially in parallel with creating slices for each pillar of the next series of data segments X+1 through Y and sending the slices for storage to storage set B. In other words, with two storage sets the DS processing unit  16  sends slices for a first series of data segment numbers to storage set A while in parallel sending slices for a second series of data segment numbers to storage set B. The DS processing unit  16  subsequently retrieves the data object by retrieving slices for each pillar of a first series of data segments from storage set A substantially in parallel with retrieving slices for each pillar of the next series of data segments from storage set B. 
         [0098]    In a third embodiment, the DS processing unit  16  divides the data object into two or more sub-files, labeling them with the same filename but with different vault generations, creating slices for each pillar of the first sub-file and sending the slices for storage to storage set A substantially in parallel, or concurrently, with creating slices for each pillar of the next sub-file (e.g., different vault generation) and sending the slices for storage to storage set B. In other words, with two storage sets the DS processing unit  16  sends slices for a first sub-file (e.g., vault gen  1 ) to storage set A while in parallel sending slices for a second sub-file (e.g., vault gen  2 ) to storage set B. The DS processing unit  16  subsequently retrieves the data object by retrieving slices for each pillar of the first sub-file (e.g., vault gen  1 ) from storage set A substantially in parallel with retrieving slices for each pillar of the second sub-file (e.g., vault gen  2 ) from storage set B. The DS processing unit then combines the sub-files to recreate the data object. 
         [0099]      FIG. 9  is a schematic block diagram of an embodiment of a distributed storage (DS) unit  36  that includes a storage unit control module  109  and a plurality of memories that includes memory  1  through memory m. The storage unit control module  109  may be implemented with the computing core of  FIG. 2 . The memories may be one or more of a magnetic hard disk, NAND flash, read only memory, optical disk, and/or any other type of read-only, or read/write memory. The memories may be implemented as part of or outside of the DS unit  36 . For example, memory  1  may be implemented in the DS unit  36  and memory  2  may be implemented in a remote server (e.g., a different DS unit operably coupled to the DS unit  36  via the network). 
         [0100]    The storage unit control module  109  may be operably coupled to the computing system utilizing the DSnet interface  111  via the network. The storage unit control module  109  may receive a EC data slice to store via the DSnet interface  111 . Note that the slice may be received as part of a batch of slices (e.g., slices of the same pillar for the same data segment). In an embodiment, the storage unit control module  109  determines where (e.g., which address on which of the memories) to store the received EC data slices. The determination may be based on one or more of number of slices in the batch, slice sizes, metadata associated with the slices, a type of data indicator, a priority indicator, available memory, memory performance data, memory cost data, and/or any other parameter to facilitate desired levels of efficiency and performance. 
         [0101]    The storage unit control module  109  may determine to utilize one or more memories  1 -m for the slice batch. The storage unit control module  109  may determine to evenly distribute the slice batch across the selected memories or the storage unit control module  109  may determine to vary the number of slices of the slice batch stored in each of the selected memories. For example, the storage unit control module  109  may select memory  2  to store all of the received slice batch since the number of slices in the slice batch was below a threshold (e.g., a relatively small batch). In another example, the storage unit control module  109  may select memories  1 - 4  to evenly distribute the received slice batch since the number of slices in the slice batch was above a threshold (e.g., a relatively large batch). The storage unit control module  109  maintains a local virtual DSN address to physical location table to keep track of the locations of the slices upon storage such that the slices may be retrieved from the proper memory upon subsequent retrievals. In other words, the table lists the memory number and memory location for each slice name. Note that subsequent retrievals may enjoy a more favorable net retrieval time since memories  1 - 4  can simultaneously retrieve slices. The method to determine the memories is discussed in greater detail with reference to  FIG. 10 . 
         [0102]      FIG. 10  is a flowchart illustrating the storing of distributedly stored data where the storage unit control module of the DS storage unit receives slices, determines which memories to select for storage of the slices, and stores the slices in the selected memories. 
         [0103]    The method  1010  begins at block  1013 , where the storage unit control module receives the slice from one or more of the DS processing unit, the storage integrity processing unit, the DS managing unit, and/or the user device. Note that the slice may be received as part of a batch of slices (e.g., slices of the same pillar for the same data segment). The storage unit control module may count the number of slices to determine the number of slices in the slice batch. The slice may have an appended metadata indicating a priority, a data type, a user ID, a security level, a speed of retrieval requirement, a performance requirement, a reliability requirement, and/or a cost requirement. 
         [0104]    As illustrated by blocks  1015  and  1017 , the storage unit control module determines a memory utilization method based on one or more of number of slices in the slice batch, slice sizes, metadata appended and/or associated with the slices, a performance requirement, a type of data indicator, a priority indicator, available memory, memory performance data, memory cost data, and/or any other parameter to facilitate desired levels of efficiency and performance. 
         [0105]    In an embodiment, the storage unit control module determines the memory utilization method to select one memory or more than one memory based in part on the number of slices in the batch. For example, the storage unit control module may select one memory when the number of slices in the slice batch is below a threshold, and more than one memory when the number of slices in the slice batch is above a threshold. As illustrated by block  1019 , the storage unit control module stores the slices in the one memory and updates the local virtual DSN address to physical location table when storage unit control module determines the memory utilization method to be one memory. 
         [0106]    As illustrated by block  1021 , the storage unit control module determines the distribution method when the storage unit control module determines the memory utilization method to be more than one memory. The storage unit control module may determine the distribution method by selecting the number of memories based on one or more of the number of slices in the slice batch, the slice sizes, the priority, the performance requirements, and/or the memory performance data. For example, the storage unit control module may select a higher number of memories when the performance requirements are more demanding (e.g., faster retrieval time as compared to the average required retrieval time). The storage unit control module may select an uneven distribution of the slices between the memories based on the memory performance data (e.g., actual capabilities) of each memory. As illustrated by block  1023 , the storage unit control module stores the slices substantially in parallel in the memories and updates the local virtual DSN address to physical location table. 
         [0107]    Note that the storage unit control module references the local virtual DSN address to physical location table to determine which memories the slices are located in upon receiving a retrieval request from a requester (e.g., from DS processing). The storage unit control module may retrieve the slices substantially in parallel across two or more memories when the slices for a segment are stored in the two or more memories. The storage unit control module sends the retrieved slices to the requester. Further note that the retrieval time performance of the DS unit may be improved when the slices are substantially retrieved in parallel from the memories. 
         [0108]      FIG. 11  is a schematic block diagram of another embodiment of a computing system that may provide improved security by utilizing onion routing to communicate EC data slices. 
         [0109]    The computing system includes the DS processing unit  16 , an onion layer of DS units  5 - 10 , and a storage set  1110  of DS units  1 - 4 . In another embodiment, the DS processing unit may be replaced with the DS processing in any one or more of the user device, the storage integrity processing unit, and/or the DS managing unit. The storage set  1110  may include any number of DS units that comprise the pillars for one or more vaults. For example, in a 16/10 DSN system the storage set includes 16 DS units while in a 4/3 DSN system the storage set includes 4 DS units as shown. 
         [0110]    The DS processing unit  16  creates a layer  1  package to communicate through the onion layer to the storage set. The layer  1  package includes one or more of a message to be communicated to the storage set and slices to be stored in the storage set. The message may include a command such as store, retrieve, status, and delete along with a slice name. For example, the layer  1  package may include a store command and pillar  1  slices to store in DS unit  1 , pillar  2  slices to store in DS unit  2 , pillar  3  slices to store in DS unit  3 , and pillar  4  slices to store in DS unit  4 . 
         [0111]    The DS processing unit  16  creates the layer  1  package based on a determination of a number of layers of a route, and a determination of which DS units (e.g., route nodes) are along the route, or in the chain of DS units. The DS processing unit  16  performs the determination of the number of route layers and which DS unit nodes based on one or more of a security requirement, a retrieval performance requirement, a random number, a timer, a predetermined sequence, a user ID, a vault ID, a type of data indicator, DS unit availability, DS unit performance history, a network loading indicator, a regional path requirement, and/or a priority indicator. For example, the DS processing unit may select three layers and DS units  5 ,  6 , and  8  to serve as the nodes in the onion layer when a moderate security requirement and a moderate retrieval performance requirement is indicated. The DS processing unit may select more layers when the security requirement is for greater security. Note that each of the DS units in the onion layer can also be considered to part of a chain of DS units, with the first DS unit representing the first layer, the first link, etc., and the end DS unit representing the innermost onion layer, the last link in the chain, and so on. 
         [0112]    Note that the route, or chain, may traverse any number of one or more DS unit nodes in the onion layer. The DS processing unit  16  sends the layer  1  package to an entry node DS unit in the onion layer. The entry node DS unit may pass the package to an intermediate node which may pass the package through a series of intermediate nodes. Note that the route may repeat DS unit nodes. The last intermediate node may pass the package to an exit node. In an embodiment, the entry node and the exit node may be the same DS unit (e.g., no intermediate nodes). 
         [0113]    In another embodiment, the DS processing unit  16  may create two or more packages with two or more selections of layers and nodes for the same data segment or data object to send slices through the onion layer to the storage set. In other words, the DS processing unit  16  may select more than one route where some of the slices are split in a first route while other slices traverse a different route. In an embodiment, the DS processing unit may send the two or more packages to two or more entry nodes as the first layer in the onion layer. For example, the DS processing unit  16  may send a first package of data segment  100  to entry node DS unit  7  and a second package of data segment  100  to entry node DS unit  10 . In another embodiment, the DS processing unit  16  may send the two or more packages bundled as one initial package to one entry node as the first layer in the onion layer followed by an intermediate node that may split out the two or more packages and forward the two or more packages to other nodes. For example, intermediate node DS unit  5  may split out a first package of data segment  100  and send it to exit node DS unit  8  and DS unit  5  may split out a second package of data segment  100  and send it to exit node DS unit  10 . In yet another embodiment, the intermediate node may combine packages and forward a combined package. 
         [0114]    The DS processing unit  16  creates the layer  1  package by creating a series of nested onion layer packages. The DS processing unit  16  starts with creating final layer package (e.g., the layer  3  package in the example). The DS processing unit  16  creates the message for the target storage set (e.g., the command and/or EC data slices for storage), appending the exit node designation (e.g., DS unit  8 ) and encrypting all that using the public key for the exit node (e.g., DS unit  8 ) to produce the layer  3  package. Next, the DS processing unit  16  creates the next-to-last layer package (e.g., the layer  2  package in the example). In the example, the DS processing unit  16  creates the layer  2  package by appending the intermediate node designation (e.g., DS unit  5 ) to the layer  3  package and encrypting all that using the public key for the intermediate node (e.g., DS unit  5 ) to produce the layer  2  package. Next, the DS processing unit  16  creates the entry node layer package (e.g., the layer  1  package in the example). In the example, the DS processing unit  16  creates the layer  1  package by appending the entry node designation (e.g., DS unit  6 ) to the layer  2  package and encrypting all that using the public key for the entry node (e.g., DS unit  6 ) to produce the layer  1  package. The flow described above is depicted graphically in  FIG. 12 . The DS processing unit  16  method to create packages is discussed in greater detail with reference to  FIG. 13 . 
         [0115]    The DS units may store, delete, and retrieve data slices as previously discussed. In an embodiment, the DS units of the onion layer may operate in accordance with one or more roles including the entry node, intermediate node, and/or exit node. The DS unit determines the role based on decrypting and inspecting a received package. The DS unit decrypts the received package utilizing its private key (e.g., the private key is paired with the public key as utilized previously by the DS processing unit to create the package). The DS unit inspects the decrypted package to determine if it contains the end message or a forwarding address designation (e.g., of the next node) appended to yet another encrypted package. Note that the DS unit may not be able to decrypt the next encrypted package since that encrypted package utilizes encryption of the next node. 
         [0116]    The DS unit sends the message to the targeted storage set when the DS unit determines its role is the exit node. The DS unit sends the message to the next targeted onion layer node when the DS unit determines its role is the entry or intermediate node. The DS unit method to process packages is discussed in greater detail with reference to  FIG. 14 . 
         [0117]      FIG. 12  is a block diagram of an embodiment of layered message creation where the DS processing unit combines one or more of a command and/or EC data slices from a data object into a message that is wrapped in a series of encrypted layer packages. The graphical illustration depicts the route example of  FIG. 11  as was previously discussed. 
         [0118]      FIG. 13  is a flowchart illustrating the creation of a layered message where the DS processing unit prepares the package to send through the onion layer to the storage set. 
         [0119]    The method begins with the step  1363 , where the DS processing unit creates the message. The message may include the command (e.g., store, retrieve, delete, status, etc.) and may include EC data slices (e.g., created from a data object) for one or more pillars and/or supplementary information (e.g., metadata about the data object). 
         [0120]    As illustrated by block  1365 , the DS processing unit determines the number of route layers based on one or more of a security requirement, a retrieval performance requirement, a random number, a timer, a predetermined sequence, a user ID, a vault ID, a type of data indicator, DS unit availability, DS unit performance history, a network loading indicator, a regional path requirement, and/or a priority indicator for one or more of the other factors. For example, the DS processing unit may select one layer when the retrieval performance requirement indicates a faster than average required retrieval time and the retrieval performance requirement has a high priority indicator. 
         [0121]    As illustrated by block  1367 , the DS processing unit determines the route based on one or more of a security requirement, a retrieval performance requirement, a random number, a timer, a predetermined sequence, a user ID, a vault ID, a type of data indicator, DS unit availability, DS unit performance history, a network loading indicator, a regional path requirement, and/or a priority indicator for one or more of the other factors. The route may include one or more entry nodes, intermediate nodes, and exit nodes. The route may change from data segment to data segment or for each slice. For example, the DS processing unit may select a route through three different geographic regions when the regional path requirement requires that the route traverse at least three regions and the regional path requirement has a high priority indicator. In another embodiment, the DS processing unit may select two routes and divide the package into two packages as previously discussed. 
         [0122]    As illustrated by block  1369 , the DS processing unit creates the package starting with the exit node. As illustrated by block  1371 , the DS processing unit creates the package for a layer by appending the address of the target layer node to the message (or previous package for subsequent loops) and encrypting that together utilizing the public key for that layer. 
         [0123]    As illustrated by blocks  1373  and  1375 , the DS processing unit determines if all layers are done by comparing the just completed layer with the entry node layer. The method branches back to block  1371 , where the DS processing unit creating the package for a layer (the next layer towards the entry node) when the DS processing unit determines that all layers are not done. 
         [0124]    As illustrated by block  1377 , the DS processing unit sends the package to the entry node(s) when the DS processing unit determines that all layers are done. 
         [0125]      FIG. 14  is a flowchart illustrating the processing of a layered message where the DS unit processes an incoming received package in accordance with the DS unit onion layer role. The DS unit onion layer roles include the entry node, the intermediate node, and/or the exit node. The DS unit determines the role based on decrypting and inspecting a received package. 
         [0126]    As illustrated by block  1479 , the DS unit receives the package from the DS processing unit or another DS unit (e.g., and intermediate node). As illustrated by block  1481 , the DS unit decrypts the received package utilizing its private key (e.g., the private key is paired with the public key as utilized previously by the DS processing unit to create the package). 
         [0127]    As illustrated by blocks  1483  and  1485 , the DS unit determines if it is the exit node by inspecting the decrypted package. The determination may be based on the package contents including the end message or a forwarding address designation (e.g., of the next node) appended to yet another encrypted package. 
         [0128]    As illustrated by block  1491 , the DS unit determines the target DS unit(s) of the storage set when the DS unit determines it is the exit node. The determination may be based on inspecting the message to read the DSN addresses. As illustrated by block  1493 , the DS unit sends the message to the targeted DS unit(s) of the storage set. 
         [0129]    As illustrated by block  1487 , the DS unit determines the next layer destination when the DS unit determines it is not the exit node (e.g., it is an intermediate node or the entry node). The determination may be based on inspecting the message to read the designation of the next layer node. As illustrated by block  1489 , the DS unit sends the message to the next layer node. The process repeats as described above until the package reaches the exit node. 
         [0130]    In addition to the method described previously with regards to sending an outbound message from an originator node to the endpoint distributed storage unit as encoded multiple nested layers through a plurality of intermediate distributed storage units, the methods described below may be utilized to send a response message inbound from the endpoint distributed storage unit to the originator node. The method begins with the step where a processing module of the intermediate distributed storage unit saves the outbound information from the outbound message as it passes through the intermediate distributed storage unit. 
         [0131]    The outbound information may include a distributed storage unit identifier corresponding to the distributed storage unit that the outbound message was received from, a distributed storage unit identifier corresponding to the distributed storage unit that the outbound message was sent to next, a message identifier, and/or a decoded key. Note that the processing module may produce the decoded key by decrypting at least a portion of the outbound message utilizing a private key associated with the distributed storage unit. In some embodiments, the processing module can obtain the outbound information from one or more of a lookup, a list, a predetermination a command, a message, or another suitable source. 
         [0132]    The method continues with the step where the processing module of the intermediate distributed storage unit receives the inbound message (e.g., a response message to a previous message). The processing module determines where to forward the response message based on a response message identifier, a distributed storage unit identifier corresponding to the distributed storage unit that the inbound message was received from, and the outbound information. For example, the processing module determines to forward the message to DS unit  5  when the response message identifier correlates to a message identifier of the outbound information indicating that the distributed storage unit previously forwarded the outbound message from DS unit  5  to DS unit  2  and the inbound message was received from DS unit  2 . The processing module determines the decoded key based on the outbound information (e.g., the previously stored decoded key). The processing module encrypts at least a portion of the inbound message utilizing the decoded key. 
         [0133]    The above method repeats such that the inbound message may traverse a plurality of intermediate distributed storage units where each of the plurality of distributed storage units determines where to forward the inbound message, encrypts the inbound message, and forwards the inbound message. Some embodiments of the method end when the inbound message reaches the originator node (e.g., a DS processing unit that sent the original outbound message including each of the plurality of keys utilized by each of the intermediate distributed storage units). 
         [0134]    The following method describes the decoding of a received inbound message by a processing module where the inbound message contains a plurality of layers. The processing module may be implemented in a user device, a DS processing unit, the storage integrity processing unit, a DS managing unit, and/or a DS unit. For example, the processing module can be implemented in a DS processing unit that originated an outbound message that corresponds to the received inbound message when the inbound message contains a response message to a message contained in the outbound message. 
         [0135]    The method begins with the step where the processing module receives an inbound message from an intermediate distributed storage unit. The processing module determines a message to which the response message corresponds based on a response message identifier that can be included within the inbound message, a lookup table that correlates message identifiers and response message identifiers, and/or the distributed storage unit identifier of the distributed storage unit from which the inbound message was received. The processing module determines a plurality of keys and an order in which the plurality of keys is to be applied to the message based on the message identifier and a lookup table that correlates message identifiers with keys. 
         [0136]    The method continues with the step where the processing module decrypts the inbound message utilizing one of the plurality of keys in accordance with the order determined for the plurality of keys. The method repeats the step to decrypt the inbound message utilizing each of the plurality of keys in accordance with the plurality of keys order to produce an unencrypted inbound message. The processing module determines the response message based on the unencrypted inbound message. 
         [0137]    As may be used herein, the terms “substantially” and “approximately” provides an industry-accepted tolerance for its corresponding term and/or relativity between items. Such an industry-accepted tolerance ranges from less than one percent to fifty percent and corresponds to, but is not limited to, component values, integrated circuit process variations, temperature variations, rise and fall times, and/or thermal noise. Such relativity between items ranges from a difference of a few percent to magnitude differences. As may also be used herein, the term(s) “coupled to” and/or “coupling” and/or includes direct coupling between items and/or indirect coupling between items via an intervening item (e.g., an item includes, but is not limited to, a component, an element, a circuit, and/or a module) where, for indirect coupling, the intervening item does not modify the information of a signal but may adjust its current level, voltage level, and/or power level. As may further be used herein, inferred coupling (i.e., where one element is coupled to another element by inference) includes direct and indirect coupling between two items in the same manner as “coupled to”. As may even further be used herein, the term “operable to” indicates that an item includes one or more of power connections, input(s), output(s), etc., to perform one or more its corresponding functions and may further include inferred coupling to one or more other items. As may still further be used herein, the term “associated with”, includes direct and/or indirect coupling of separate items and/or one item being embedded within another item. As may be used herein, the term “compares favorably”, indicates that a comparison between two or more items, signals, etc., provides a desired relationship. For example, when the desired relationship is that signal  1  has a greater magnitude than signal  2 , a favorable comparison may be achieved when the magnitude of signal  1  is greater than that of signal  2  or when the magnitude of signal  2  is less than that of signal  1 . 
         [0138]    The present invention has also been described above with the aid of method steps illustrating the performance of specified functions and relationships thereof. The boundaries and sequence of these functional building blocks and method steps have been arbitrarily defined herein for convenience of description. Alternate boundaries and sequences can be defined so long as the specified functions and relationships are appropriately performed. Any such alternate boundaries or sequences are thus within the scope and spirit of the claimed invention. 
         [0139]    The present invention has been described above with the aid of functional building blocks illustrating the performance of certain significant functions. The boundaries of these functional building blocks have been arbitrarily defined for convenience of description. Alternate boundaries could be defined as long as the certain significant functions are appropriately performed. Similarly, flow diagram blocks may also have been arbitrarily defined herein to illustrate certain significant functionality. To the extent used, the flow diagram block boundaries and sequence could have been defined otherwise and still perform the certain significant functionality. Such alternate definitions of both functional building blocks and flow diagram blocks and sequences are thus within the scope and spirit of the claimed invention. One of average skill in the art will also recognize that the functional building blocks, and other illustrative blocks, modules and components herein, can be implemented as illustrated or by discrete components, application specific integrated circuits, processors executing appropriate software and the like or any combination thereof.