Patent Publication Number: US-9905261-B2

Title: Media mobility unit (MMU) and methods of use thereof

Description:
BACKGROUND 
     The present invention relates to data storage systems using media cartridges and media libraries, and more particularly, to a media mobility unit for moving media cartridges between media libraries. 
     Media libraries serve as practical solutions to the massive data storage and redundancy requirements of modern computing operations. Media libraries host a finite number of media volumes for storing data, and typically these volumes are classified as tape or disk, depending on the data storage format. In order to meet access and redundancy requirements, many operations employ multiple libraries at multiple access points. When using a plurality of access points without universal or shared accessibility, physical volumes are occasionally unmounted from one media library and mounted to another in order to provide access to the requested volume. In addition, new volumes may be occasionally be used to replace full volumes and permit storage of additional new data. 
     Typically, these physical movements are performed by human technicians manually entering a command to unmount a source volume from a source library, receiving the requested volume from the source library, carrying the source volume to a destination library, placing the source volume in a destination library receptacle, and entering a command to mount the source volume in the destination library. 
     Some recent approaches have endeavored to automate the process of unmounting, receiving, transferring, and mounting volumes from one media library to another by way of mechanical arms, tracks, and/or rails to transfer volumes between two libraries. In these approaches, however, media libraries must be in sufficiently close physical proximity such that the arm, track, and/or rails may span the distance between source and destination media libraries. This proximity requirement places physical limits on the arrangement of media libraries in a physical space. In addition, since each library must be attached to an arm, track, or railing as well as a mechanism for moving media along the arm, track, or railing, it can be very expensive to replace existing media libraries with those having the requisite mobility mechanisms. Even if media libraries may be retrofit with such mobility devices, interfacing multiple libraries becomes increasingly problematic as the number of libraries increases, again due in large part to spatial limitations. 
     However, as computational resources and data security continue to accrue significance in this information age, current approaches to efficiently move media volumes between media libraries is becoming increasingly unsuitable for evolving performance requirements. Therefore, it would be a useful endeavor to develop a system and method for providing mobility to a network of media libraries without incurring the enormous cost of replacing current libraries or the spatial limitations imposed by permanent tracks, arms, and/or rails connecting media libraries in physical proximity. Furthermore, it would be advantageous to eliminate the spatial limitations and proximity requirements of currently envisioned media mobility systems. 
     SUMMARY 
     In one embodiment, a data storage system includes: a source media library configured to send a message to a destination media library when a media cartridge from the source media library is sent to the destination media library using a media mobility unit (MMU). The MMU includes a media cartridge holding portion for storing media cartridges, and the source media library is configured to receive a message from the destination media library when the destination media library receives the media cartridge sent from the source media library to the destination media library using the MMU. 
     In another embodiment, a data storage system includes: a destination media library configured to receive a message from a source media library when a media cartridge from the source media library is sent to the destination media library using a media mobility unit (MMU). The MMU includes a media cartridge holding portion for storing media cartridges, and the destination media library is configured to send a message to the source media library when the destination media library receives the media cartridge from the source media library. 
     In yet another embodiment, a method for transporting a media cartridge includes: receiving one or more media cartridges from a source media library; storing the one or more media cartridges in a media mobility unit (MMU); sensing at least an approximate location of the MMU; transporting the one or more media cartridges between a destination media library and the source media library; and transferring the one or more media cartridges from the MMU to the destination media library. 
     Other aspects and embodiments of the present invention will become apparent from the following detailed description, which, when taken in conjunction with the drawings, illustrates by way of example the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a schematic of a media mobility unit from a side view, according to one embodiment. 
         FIG. 2  illustrates a schematic of a media mobility unit from a distal view, according to one embodiment. 
         FIG. 3  illustrates a schematic of a media library from a front view, according to one embodiment. 
         FIG. 4  illustrates a schematic of a media mobility unit docked with a media library from a side view, according to one embodiment. 
         FIG. 5  illustrates a diagrammatic layout of a media library being serviced by a media mobility unit, according to one embodiment of a grid-based location system (GBLS). 
         FIG. 6  is a flow diagram of a method, according to one embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     The following description is made for the purpose of illustrating the general principles of the present invention and is not meant to limit the inventive concepts claimed herein. Further, particular features described herein can be used in combination with other described features in each of the various possible combinations and permutations. 
     Unless otherwise specifically defined herein, all terms are to be given their broadest possible interpretation including meanings implied from the specification as well as meanings understood by those skilled in the art and/or as defined in dictionaries, treatises, etc. 
     It must also be noted that, as used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless otherwise specified. 
     According to one general embodiment, a data storage system includes a source media library configured to send a message to a destination media library when a media cartridge from the source media library is sent to the destination media library using a media mobility unit (MMU) comprising a media cartridge holding portion for storing media cartridges, wherein the source media library is configured to receive a message from the destination media library when the destination media library receives the media cartridge sent from the source media library to the destination media library using the MMU. 
     In another general embodiment, a data storage system includes a destination media library configured to receive a message from a source media library when a media cartridge from the source media library is sent to the destination media library using a media mobility unit (MMU) comprising a media cartridge holding portion for storing media cartridges, wherein the destination media library is configured to send a message to the source media library when the destination media library receives the media cartridge from the source media library. 
     In another general embodiment, a MMU includes a media cartridge holding portion for storing media cartridges, a sensing mechanism for sensing at least an approximate location of the holding portion in relation to other objects, a drive mechanism for moving the holding portion from a source media library to a destination media library, and a power source electrically coupled to at least one of the sensing mechanism and the drive mechanism for providing current to the at least one of the drive mechanism and the sensing mechanism. 
     In yet another general embodiment, a method for transporting a media cartridge includes receiving one or more media cartridges from a source media library, storing the one or more media cartridges in a MMU, sensing at least an approximate location of the MMU, and transporting the one or more media cartridges to a destination media library. 
     Referring now to the figures,  FIG. 1  shows a schematic of a media mobility unit (MMU)  100  from a side view, according to one embodiment. As shown, the MMU  100  includes three portions: a power source portion  102 , a connecting portion  104 , and a cartridge holding portion  106 . The MMU  100  also includes a mechanism for moving the unit, shown as a pair of front drive wheels  118  (only one wheel is visible due to the drawing angle) capable of providing forward or reverse motion to the unit independently to facilitate motion, turning, and pivoting, and a single castor wheel  120  adapted for providing support to the MMU  100 . In another embodiment, the drive wheels  118  may each provide a forward or reverse motion to the MMU  100  while the rear wheel  120  provides a direction. In yet another embodiment, there may be more than one rear wheel  120 , which may or may not provide direction to the MMU  100 . 
     With continuing reference to  FIG. 1 , the power source portion  102  may include a rechargeable power source, such as a rechargeable battery, and may be adapted for being recharged at designated stations, such as while being docked at a media library. Furthermore, the power source portion  102  may include additional components, such as a position sensor or laser reader  124 , swiveling wheels  120 , etc. In one embodiment, the power source portion  102  may include non-rechargeable batteries that are replaceable, a power source that operates from contact with a power supply (such as one used for light rail train engines), or any other power source as would be understood by one of skill in the art upon reading the present descriptions. 
     In one embodiment, a laser reader  124  extends proximally from the rear side of the MMU  100 . The laser reader  124 , as shown, is adapted for reading one or more barcodes  122  which may be located at positions along the floor, on walls, on the ceiling, in a grid, or anywhere else that the laser reader  124  is capable of reading them as the MMU  100  passes by. The barcodes  122  may have any dimension and may comprise any pattern adapted for being recognized by the laser reader  124 . In one embodiment, the bar codes  122  may be positioned at each floor tile (such as floor tiles measuring 24 in.×24 in. or any other dimension) such that movement of the MMU  100  is detectable at each floor tile. Of course, many other barcode  122  positions are possible, and the positioning of the barcodes  122  is not meant to be limited in any way by this description. 
     In more embodiments, more than one laser reader  124  may be used, and each laser reader  124  may be positioned at any location on the MMU  100  that facilitates the reading of the barcodes  122 , according to various embodiments, such as on the media cartridge portion  106 , on the connecting portion  104 , on the bottom, on the top, on one or more sides, etc. As the MMU  100  travels from a source media library to a destination media library, the barcodes  122  may be read by the laser reader  124  such that a current position of the MMU  100  is detectable during the transit, such that proper retrieval and delivery of media cartridges may be accomplished. 
     In another approach, the laser reader  124  may function as a position sensor to determine the position of the MMU  100 . Of course, alternate embodiments may utilize similar variations of a barcode and laser reader to navigate between and identify various media libraries in a storage system. Furthermore, alternate embodiments may utilize similar variations of a barcode and laser reader to determine the position of the MMU  100 . 
     In another embodiment, the MMU  100  may comprise a radio frequency identification (RFID) device to determine positional information of the MMU  100 , such as an RFID reader. In this embodiment, RFID tags may be positioned throughout a storage system such that each media library is represented, and paths between the media libraries are designated by the RFID tags. 
     According to one embodiment, the swivel wheels  120  protrude from the bottom of the MMU  100  near the rear and provide pivoting capability and lateral mobility to the MMU  100 . Any type of pivoting wheel may be used, such as a castor wheel, a wheel coupled to a swiveling base, ball bearings, etc. 
     Referring still to  FIG. 1 , the cartridge holding portion  106  may be located at a distal end of the MMU  100  and coupled to the power source portion  102  via the connecting portion  104 . In some embodiments, a connecting portion  104  is not used when the power source portion  102  connects to the cartridge holding portion  106  directly. The cartridge holding portion  106  may further be connected to the drive wheels  118 , which may confer longitudinal mobility to the MMU  100  by driving it along a surface upon receiving a request to retrieve or store a media cartridge or move to a new location in a grid-based location system (GBLS). 
     The cartridge holding portion  106  additionally includes several components adapted for conferring various capabilities to the MMU  100 . 
     In one approach, the cartridge holding portion  106  includes sensors. For example, one or more proximity sensors  110  may be adapted for conveying information about proximity of nearby objects to the MMU  100  as it travels between media libraries. In another example, one or more fiducial sensors  108  may be coupled to the cartridge holding portion  106  that may be adapted for communicating alignment information as the MMU  100  attempts to interface with a media library, which is equipped with a corresponding sensor or alignment mechanism. 
     Additionally, the cartridge holding portion  106  may comprise locking pins  116  located at a lower distal end of the MMU  100  and adapted for engaging locking pin slots of media libraries upon docking with the media library in order to avoid unexpected or undesirable motion during a media transfer operation. Alternatively, the cartridge holding portion  106  may include locking pin slots  116  adapted for receiving locking pins deployed from a media library upon docking the MMU  100  with the media library in order to avoid unexpected or undesirable motion during a media transfer operation. In either case, the locking pins and locking pin slots may be constructed and operate in any manner as known to one having ordinary skill in the art. 
     Furthermore, in one embodiment, there may be a power charger  114  located on a distal end of the MMU  100  and adapted for charging the power source portion  102  of the MMU  100  upon docking with a media library. 
     With continuing reference to  FIG. 1 , the cartridge holding portion  106  may include a communication input/output (I/O)  112  for receiving input data from a media library and delivering output data to a media library. This I/O connection  112  may be used for transferring instructions from a source library to the MMU  100  that instructs the MMU  100  to travel to a destination library located remotely from the source media library to move a media cartridge therebetween. Of course, any other instructions may be provided to the MMU  100  as would be understood by one of skill in the art upon reading the present descriptions. The I/O connection may be of any type as would be known in the art. 
     According to one approach, the source media library (such as from a library control manager) may send a message to the destination media library and/or some other system (such as a storage controller) that the source media library is sending a media cartridge to the destination media library. When the media cartridge is received by the destination media library, the destination media library may send a message to the source media library and/or some other system that the media cartridge from the source media library was received at the destination media library. This ensures that there is a “handshake” between the media libraries such that a media cartridge in transit is not lost during the transportation thereof. Otherwise, once the media cartridge was sent from the source media library, there would be no evidence of its intended delivery or that it left the source media library. Of course, other methods may be used to ensure that media cartridge visibility and accountability is maintained during the transportation process, as would be understood by one of skill in the art upon reading the present descriptions. 
     In some further approaches, there may be a time period associated with when the media cartridge is sent from the source media library and when it is delivered to the destination media library such that if the message indicating the media cartridge&#39;s arrival is not received by the source media library and/or some other system prior to the expiration of this time period, an alert may be issued that a problem has arisen in the transportation of the media cartridge. In response to this alert, a technician, administrator, or some other suitable person may determine what has caused the delay in the delivery of the media cartridge. 
     According to one embodiment, the source media library may be configured to send a message to a destination media library when a media cartridge from the source media library is sent to the destination media library, and the source media library may be configured to receive a message from the destination media library when the destination media library receives the media cartridge from the source media library. 
     In another embodiment, the destination media library may be configured to receive a message from a source media library when a media cartridge from the source media library is sent to the destination media library, and the destination media library may be configured to send a message to the source media library when the destination media library receives the media cartridge from the source media library. 
     In one approach, the cartridge holding portion  106  may include one or more cartridge storage devices. The cartridge storage devices include a plurality of slots capable of securely holding media volumes during MMU  100  motion between media libraries, as will be described in reference to  FIG. 2 . 
     Referring again to  FIG. 1 , according to one embodiment, a MMU  100  comprises a media cartridge holding portion  106  for storing media cartridges, at least one sensing mechanism  108  and/or  110  for sensing at least an approximate location of the holding portion  106  in relation to other objects, a drive mechanism  118  for moving the holding portion  106  from a source media library to a destination media library, and a power source  102  electrically coupled to at least one of the sensing mechanism  108  and/or  110  and the drive mechanism  118  for providing current to the at least one of the drive mechanism  118  and the sensing mechanism  108  and/or  110 . Of course, power may also be supplied to other components of the MMU  100 , and other components may exist, as described previously. 
     Referring now to  FIG. 2 , in one embodiment the cartridge holding portion  106  of the MMU may have the capability to hold various types of media cartridges, such as magnetic tape cartridges (e.g., linear tape-open (LTO) compatible tape cartridges and/or  3592  format tape cartridges, etc.), disc cartridges, etc. In one approach, the cartridge holding portion  106  may include more than one configuration of cartridge storage devices  202  and/or  204 . As shown, the cartridge holding portion  106  includes a plurality of storage slots  206 , each capable of storing a media volume from a media library. In the embodiment shown in  FIG. 2 , the cartridge holding portion  106  is depicted with a first cartridge holder  202  and a second cartridge holder  204 . While this embodiment depicts a cartridge holding portion  106  with two types of cartridge holders, alternative embodiments may hold any number of cartridge holders, limited only by the physical dimensions and docking capabilities of the associated media libraries. 
     In operation, the cartridge storage devices  202  and/or  204  are adapted for interfacing with a picker of a media library in order to transfer media cartridges between the MMU and the media library. In this manner, the MMU may securely store the retrieved volume(s) in the cartridge storage device  202  and/or  204 , retrieve the stored volume(s) upon arrival at a destination library, and deliver the retrieved volume(s) to a destination media library, in one approach. 
     Referring now to  FIG. 3 , a media library  300  is shown, according to one embodiment. As depicted, the media library  300  includes a housing  302 , an operator panel  304 , an I/O station  306 , and a docking station  312 . The docking station  312  may further include one or more doors  308 , and a fiducial  310 . In operation, the docking station  312  may serve as an interface point for one or more MMUs servicing a GBLS with associated media libraries  300 . 
     In another embodiment, and with continuing reference to  FIG. 3 , the one or more doors  308  may be configured to open via spring-loading or other automated opening mechanisms as known to one having ordinary skill in the art. Other embodiments may be adapted to automatically trigger the opening mechanism and open the doors  308  when a MMU begins to interface with the docking station  312  of the media library  300 . In addition, the doors  308  may similarly be configured to automatically close when a MMU detaches from the docking station  312  of the media library  300 . Alternatively, the doors  308  may be triggered to open upon successful engaging of the locking pins  116  with corresponding locking pin slots, etc. 
     Referring now to  FIG. 4 , a MMU  100  is shown interfacing with a docking station  312  of a media library  300 , according to one embodiment. As shown, the MMU  100  is docking with the media library  300  at the level where the doors are located, such that an operator would still be able to access the operator panel  304 . Of course, any configuration may be used as would be understood by one of skill in the art upon reading the present descriptions. 
     Referring now to  FIG. 5 , a GBLS  500  and corresponding MMU  100  for transporting media cartridges between a source and destination media library are shown, according to one embodiment. As shown, the GBLS  500  includes a plurality of indicators  506  on one or more surfaces, the plurality of indicators  506  being positioned to be readable by a device on the MMU  100 . In one embodiment, the indicators  506  may be barcodes, and the device for reading the indicators  506  may be a barcode reader. In another embodiment, the indicators  506  may be RFID tags, and the device for reading the indicators  506  may be a RFID reader. Of course, any other indicator and device capable of reading the indicators may be used as one of skill in the art would understand upon reading the present descriptions. 
     The indicators  506  are positioned in pathways  502  between a plurality of media libraries  300 , each media library having an associated docking station  312  and an indicator  508  designating the position of the docking station  312 . In operation, the MMU  100  may travel along a plurality of pathways  502  from a source media library to a destination media library, detect a proximate media library  300  via a proximity sensor, read a media barcode  506 , and identify whether the particular library is the appropriate destination by comparing an observed barcode value to a requested barcode value. When the MMU  100  identifies a library as the appropriate destination, it may furthermore initiate a docking sequence with the docking station  312  of the destination library. 
     Alternatively, in another embodiment, the MMU  100  may be provided with a set of addresses for each media library  300  in the GBLS  500  and additionally with appropriate travel pathways  502  for traversing the GBLS  500  from library to library. 
     In still another embodiment, the MMU may be provided with optimization algorithms such as machine-learning to maximize efficiency of media mobility according to one or more user-defined variables such as travel time, travel distance, number of pickups or deliveries, etc. In such an approach, the MMU  100  may calculate an optimum travel route according to user preferences and as understood by one having ordinary skill in the art. 
     Furthermore, in yet another embodiment, the MMU  100  may record transit data in real-time as it mobilizes media between libraries. Such data may include travel time, travel distance, number of receipts or deliveries, etc. Upon a request to move media between libraries, the MMU  100  may calculate an optimum travel protocol by comparing real-time data to optimization criteria, including user-defined criteria. 
     In some approaches, the MMU  100  may encounter one or more obstacles  504  during transit between media libraries  300 . To prevent collisions, the MMU  100  may detect such obstacles via a proximity sensor or may be instructed of the obstacle&#39;s presence by a source media library or a user, and in order to maintain operations, the MMU  100  may be instructed to return to a previous location, calculate a new route, and travel along the new route to move to the destination library. Furthermore, the MMU  100  may include obstacle locations as a factor when calculating an optimum travel protocol in order to avoid repeated collisions, backtracking, and generally to improve mobility and efficiency. 
     As envisioned, a GBLS  500  may include any number of media libraries  300  and MMUs  100  capable of being interfaced in a network environment and housed within a storage facility. The media libraries  300  may be networked in any manner as understood by one having ordinary skill in the art. 
     Furthermore, in one embodiment, a MMU  100  may sense at least an approximate location of the MMU  100  in relation to the pathways  502  and libraries  300  and transport one or more media cartridges to a destination media library. 
     In another embodiment, the MMU  100  may recharge a power source of the MMU  100  when the MMU  100  is docked at either of the source media library and the destination media library. 
     Also, in some embodiments, transporting the one or more media cartridges to the destination media library may comprise using a laser barcode reader to read a first barcode (indicator  506 ) of a plurality of barcodes  506  positioned on one or more surfaces in the grid system  500  at least between a source media library and a destination media library (any of media libraries  300 ). Each of the plurality of barcodes indicates at least an approximate location of the MMU  100  in the grid system  500 , and the MMU  100  is moved from a first barcode in a direction for causing the MMU  100  to arrive at a second barcode of the plurality of barcodes positioned in the grid system  500 , the direction being based on at least one of: a location of the first barcode and a location of the destination media library, and using the laser barcode reader to read the second barcode. 
     In more embodiments, sensing the at least an approximate location of the MMU  100  comprises at least one of sensing objects near the MMU  100 , sensing when the holding portion is aligned with a cartridge holder of the source media library, and sensing a position of the MMU  100  in the GBLS  500 . 
     Sensing the position of the MMU  100  in the GBLS  500  comprises at least one of: reading barcodes positioned on one or more surfaces in the GBLS  500  to determine the position of the MMU  100  in the GBLS  500  and using a RFID device to sense RFID devices positioned in the GBLS  500  to determine the position of the MMU  100  in the GBLS  500 . In one embodiment, the first RFID device may comprise a RFID reader capable of reading RFID tags positioned in the GBLS  500  at least between the source media library and the destination media library for indicating the position of the MMU  100  in the GBLS  500 . 
     According to one embodiment, the source media library may be configured to send a message to a destination media library when a media cartridge from the source media library is sent to the destination media library, and the source media library may be configured to receive a message from the destination media library when the destination media library receives the media cartridge from the source media library. 
     In another embodiment, the destination media library may be configured to receive a message from a source media library when a media cartridge from the source media library is sent to the destination media library, and the destination media library may be configured to send a message to the source media library when the destination media library receives the media cartridge from the source media library. 
     Referring now to  FIG. 6 , a method for using one or more MMUs  100  in a GBLS  500  is shown, according to one embodiment. The method  600  may be carried out in any desired environment and may make use of any components, including those shown in  FIGS. 1-5 , among others. 
     In operation  602 , one or more media cartridges are received from a source media library. The source media library may include a media cartridge, such as a tape cartridge, that is to be transported to a destination library. 
     In operation  604 , the one or more media cartridges are stored in a holding portion of a MMU. The holding portion of the MMU may hold other media cartridges for transport, or may hold other types of media to be transported, in various embodiments. In one approach, this may be accomplished using a picker of the source media library to capture the media cartridges from the media library and placing them in the holding portion of the MMU, as would be apparent to one of skill upon reading the present descriptions. 
     In operation  606 , at least an approximate location of the MMU is sensed. The approximate location may be sensed periodically, when encountering indicators, or in any other way as would be understood by one of skill in the art upon reading the present descriptions. 
     In one embodiment, the approximate location may be sensed based on sensing objects near the MMU, sensing when the holding portion is aligned with a cartridge holder of the source media library, and sensing a position of the MMU in a grid system. 
     In a further embodiment, sensing the position of the MMU in the grid system may comprise at least one of: reading barcodes positioned on one or more surfaces in the grid system to determine the position of the MMU in the grid system, and using a first RFID device to sense RFID devices positioned in the grid system to determine the position of the MMU in the grid system. 
     Additionally, in some approaches, the first RFID device may comprise a RFID reader capable of reading RFID tags positioned in the grid system at least between the source media library and the destination media library for indicating the position of the MMU in the grid system. 
     In operation  608 , the one or more MMUs are transported to a destination media library located remotely from the source media library where the one or more media cartridges may be delivered to the destination media library. 
     According to one embodiment, a laser barcode reader may be used to read a first barcode of a plurality of barcodes positioned on one or more surfaces in a grid system at least between the source media library and the destination media library, wherein each of the plurality of barcodes indicates at least an approximate location of the MMU in the grid system. Also, the MMU may be moved from the first barcode in a direction for causing the MMU to arrive at a second barcode of the plurality of barcodes positioned in the grid system, the direction being based on at least one of: a location of the first barcode and a location of the destination media library. Furthermore, the laser barcode reader may be used to read the second barcode to repeat the process. 
     In operation  610 , the one or more media cartridges are transferred from the holding portion of the MMU to the destination media library. In one approach, this may be accomplished using a picker of the destination media library to capture the media cartridges from the holding portion of the MMU and placing them in the media library, as would be apparent to one of skill upon reading the present descriptions. 
     According to one embodiment, the MMU may comprise a media cartridge holding portion for storing the one or more media cartridges, a sensing mechanism for sensing at least an approximate location of the MMU in relation to other objects, a drive mechanism for moving the MMU from the source media library to the destination media library, and a power source electrically coupled to at least one of the sensing mechanism and the drive mechanism for providing current to the at least one of the drive mechanism and the sensing mechanism. 
     In some embodiments, the power source may be recharged when the MMU is docked at either of the source media library and the destination media library. 
     In one embodiment, a data storage system comprises a MMU comprising a media cartridge holding portion for storing media cartridges, and a source media library. The source media library is configured to send a message to a destination media library when a media cartridge from the source media library is sent to the destination media library, and the source media library is configured to receive a message from the destination media library when the destination media library receives the media cartridge from the source media library. 
     In another embodiment, a data storage system comprises a MMU comprising a media cartridge holding portion for storing media cartridges, and a destination media library. The destination media library is configured to receive a message from a source media library when a media cartridge from the source media library is sent to the destination media library, and the destination media library is configured to send a message to the source media library when the destination media library receives the media cartridge from the source media library. 
     The data storage system may further comprise either or both of the destination media library and the source media library, wherein the destination media library may be located remotely from the source media library, according to various embodiments. 
     In another embodiment, the data storage system may further comprise the MMU and a grid system at least between the source media library and the destination media library comprising a plurality of indicators on one or more surfaces. The MMU may comprise a drive mechanism for moving the holding portion from the source media library to the destination media library, at least one proximity sensor for sensing objects near the MMU, a fiducial sensor for aligning the holding portion with a cartridge holder of at least one of the source media library and the destination media library, and at least one position reading mechanism for sensing the plurality of indicators for indicating at least an approximate location of the MMU in the grid system, wherein the MMU uses the at least the approximate location to determine a next movement of the MMU. 
     In a further embodiment, the MMU may further comprise a power source electrically coupled to the at least one proximity sensor, the fiducial sensor, the at least one position reading mechanism, and the drive mechanism for providing current to the at least one proximity sensor, the fiducial sensor, the at least one position reading mechanism, and the drive mechanism. The drive mechanism may comprise a motor for providing rotation to each of a first drive wheel and a second drive wheel independently, the first and second drive wheels positioned opposite each other near the holding portion for propelling the MMU, and a swiveling caster wheel for allowing directional changes of the MMU positioned to provide stability to the MMU. The plurality of indicators may comprise a plurality of barcodes and the at least one position reading mechanism may comprise at least one laser barcode reader for reading the plurality of barcodes positioned on the one or more surfaces in the grid system. 
     In another embodiment, a media cartridge mobility system includes a grid system (such as that described in relation to  FIG. 5 ) at least between a source media library and a destination media library located remotely from the source media library. The grid system comprises a plurality of indicators  506  (which may be barcodes, RFID devices, etc.) on one or more surfaces, the plurality of indicators being positioned to be readable by a position reading mechanism on the MMU (such as a barcode reader, an RFID reader, etc.). The system also includes a MMU (such as that described in relation to  FIG. 1 ), the MMU including a media cartridge holding portion for storing media cartridges, a drive mechanism for moving the holding portion from a source media library to a destination media library, at least one proximity sensor for sensing objects near the MMU, a fiducial sensor for aligning the holding portion with a cartridge holder of at least one of the source media library and the destination media library, at least one position reading mechanism (such as a laser barcode reader, an RFID reader, etc.) for sensing the plurality of indicators positioned on the one or more surfaces in the grid system for indicating at least an approximate location of the MMU in the grid system, wherein the MMU uses the at least the approximate location to determine a next movement of the MMU, a power source electrically coupled to the at least one proximity sensor, the fiducial sensor, the at least one position reading mechanism, and the drive mechanism for providing current to the at least one proximity sensor, the fiducial sensor, the at least one position reading mechanism, and the drive mechanism. The drive mechanism includes: a motor for providing rotation to each of a first drive wheel and a second drive wheel independently, the first and second drive wheels positioned opposite each other near the holding portion for propelling the MMU, and a swiveling caster wheel for allowing directional changes of the MMU positioned to provide stability to the MMU. 
     While various embodiments have been described above, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of an embodiment of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.