Abstract:
A data storage cartridge is equipped with write-once-read-many (WORM) write-protection. The cartridge is compatible with an existing cartridge docking station with a modification to the control logic of the docking station&#39;s control module. Specifically, the control logic is altered to recognize that sensing magnets with both sensors requires the docking station to allow data to be written to, but not erased or altered on the cartridge. In this manner, a third possibility of write-protection status is added to the two existing possibilities of full write-protection and no write-protection. Some embodiments of the invention also provide redundant indications of the WORM write-protection status of the cartridge. For example, embodiments of the invention may incorporate a radio-frequency identification (RF) tag within the cartridge and/or a status bit written into a designated WORM register within a media information header during pre-format of the cartridge media.

Description:
TECHNICAL FIELD 
     The invention relates to write-protection for data storage cartridges, such as magnetic tape cartridges. 
     BACKGROUND 
     A current data storage cartridge containing a data storage media commonly includes a magnet embedded in a slider. The slider can be manually set to one of two positions to indicate the write-protection status of the cartridge. One of the positions represents that data on the cartridge is write-protected, i.e., data cannot be erased from or written to the cartridge. The other position represents that data on the cartridge is not write-protected, meaning data can be both erased from and written to the cartridge. A docking station for the cartridge includes two magnetic sensors to detect the position of the slider when the cartridge is inserted into the docking station. One sensor is located proximate to each possible position setting of the slider. A control module of the docking station uses the slider position information as an input to execute the write-protection status of the inserted cartridge. 
     SUMMARY 
     A data storage cartridge is equipped with write-once-read-many (WORM) write-protection implemented by a docking station. For example, in some embodiments, the data storage cartridge is a magnetic tape cartridge, and the docking station is a tape cartridge drive. WORM write-protection allows data to be written to a data storage media within the cartridge, but the data cannot be modified or erased once written. Instead of having a slider with an embedded magnet having two possible positions, the cartridge includes one or more magnets covering both positions. The cartridge is compatible with an existing cartridge docking station with a modification to the control logic of the docking station&#39;s control module. Specifically, the control logic is altered to recognize that sensing magnets with both sensors requires the docking station to allow data to be written to, but not erased or altered on the cartridge. In this manner, a third possibility of write-protection status is added to the two existing possibilities of full write-protection and no write-protection. Some embodiments of the invention also provide redundant indications of the WORM write-protection status of the cartridge. For example, embodiments of the invention may incorporate a radio-frequency identification (RF) tag within the cartridge and/or a status bit written into a designated WORM register within a media information header during pre-format of the cartridge data storage media. 
     In one embodiment, a data storage cartridge comprises a cartridge housing, a data storage medium within the cartridge housing, and one or more magnets located on the cartridge housing such that two sensors of a docking station simultaneously detect magnetic fields when the data storage cartridge is interfaced with the docking station. 
     In another embodiment, a docking station for a data storage cartridge comprises an interface to receive the data storage cartridge, a first magnetic sensor that sends a first signal to indicate detection of a first magnetic field proximate to the first magnetic sensor, a second magnetic sensor that sends a second signal to indicate detection of a second magnetic field proximate to the second magnetic sensor and a control module that receives the first and second signals. The control module implements WORM write-protection for the data storage cartridge when the first magnetic sensor detects the first magnetic field and the second magnetic sensor detects the second magnetic field. 
     In another embodiment, a system comprises a data storage cartridge and a docking station for data storage cartridges. The data storage cartridge includes a cartridge housing, a data storage medium within the cartridge housing, and one or more magnets located on the cartridge housing. The docking station includes an interface to receive the data storage cartridge, a first magnetic sensor that sends a first signal to indicate detection of a first magnetic field of the one or more magnets, a second magnetic sensor that sends a second signal to indicate detection of the first magnetic field or a first magnetic field of the one or more magnets, and a control module that receives the first and second signals. The control module implements WORM write-protection for the data storage cartridge when the first and second magnetic sensors each detect magnetic fields. 
     Various embodiments of the invention may provide one or more advantages. Some embodiments provide for a docking station compatible with existing cartridges, but also compatible with WORM write-protected cartridges. For example, an existing docking station may be upgraded, e.g., a software upgrade, to support WORM write-protected cartridges. In this manner, embodiments of the invention provide cost effective techniques to implement WORM write-protection using pre-existing systems. Embodiments that include redundant write-protection indicators ensure reliable write-protection and hinder efforts to counteract such write-protection. Numerous laws, governmental regulations, industry associations and internal company policies set standards regarding record-keeping and data back-up. 
     Embodiments of the invention may also provide controllable, reliable and secure data storage integrity capable of meeting strict governmental and business standards. For example, the Sarbanes-Oxley Act of 2002 provides strict penalties for companies and individuals for intentional alteration or destruction of certain records. In light of the Sarbanes-Oxley Act and other regulations, embodiments of the invention may be useful to meet regulatory standards and to prove stored records have not been altered. 
     The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view illustrating a docking station and several data storage cartridges compatible with the docking station according to one or more embodiments of the invention. 
         FIG. 2  is a table showing the function of a WORM status bit, which can be stored on the data storage media of a data storage cartridge, such as in a media information header. 
         FIG. 3  is a flowchart illustrating a technique for determining the write-protection status of a data storage cartridge interfaced with a docking station according to an embodiment of the invention. 
         FIG. 4  is a block diagram illustrating an automated data storage cartridge library system that may implement one or more aspects of the invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a perspective view illustration of system  7  including docking station  10  and one of data storage cartridges  12 A- 12 D (cartridges  12 ), each compatible with docking station  10 . Docking station  10  can read data from a cartridge inserted in receptacle  13 . Docking station  10  includes sensors  14 A- 14 B (sensors  14 ) to read a write-protection status of an inserted cartridge. For example, sensors  14  may be magnetic field sensors, e.g., Hall-effect sensors. 
     In different embodiments, docking station  10  may read cartridges utilizing one of a variety of data storage media including, but not limited to: magnetic tape, optical discs, magneto-optic discs, magnetic discs and the like. Docking station  10  includes control module  11  that recognizes three write-protection statuses: full-write-protection, no write-protection and WORM write-protection. Control module  11  receives inputs from sensors  14 . Sensors  14  each send a signal indicating the existence or the non-existence of a magnet proximate to the sensor. Using both signals as inputs, control module  11  determines and implements the write-protection status of an inserted cartridge. Docking station  10  may be a pre-existing docking station with upgraded control logic to recognize WORM write-protection in addition to full-write-protection, no write-protection. For example, docking station  10  may include a software upgrade, to allow support of WORM write-protected cartridges. 
     When only sensor  14 A, and not sensor  14 B, detects a magnetic field from a magnet proximate to sensor  14 A and within an inserted cartridge, control module  11  recognizes that the inserted cartridge has no write-protection. Control module  11  then allows data to be written to and erased from the cartridge. When only sensor  14 B, and not sensor  14 A, detects a magnetic field, control module  11  recognizes that the inserted cartridge has full write-protection. Then control module  11  does not allow data to be written to or erased from the inserted cartridge. When both sensors  14 A and  14 B detect a magnetic field, control module  11  recognizes that the inserted cartridge has WORM write-protection. Control module  11  then allows that data can be written to, but not erased from the cartridge. 
     In various embodiments, if neither sensor  14  detects a magnetic field, control module  11  may perform one or more of the following actions: determine no cartridge is inserted, produce an error message via a user interface of a computing device, prevent access to an inserted cartridge, assume an inserted cartridge has no write-protection, assume an inserted cartridge has full write-protection, assume an inserted cartridge has WORM write-protection, look to a redundant write-protection status indicator of the cartridge to determine its write-protection status, request a user input to determine write-protection status of an inserted cartridge or perform a different action. 
     Control module  11  and the functions thereof may be implemented by executing instructions within computer-readable medium with one or more processors, discrete hardware circuitry, firmware, software executing on a programmable processor, or combinations thereof. In this manner, control module  11  is not necessarily contained within a common housing, or as a single unit, e.g., portions of control module  11  may be separate from sensors  14  and other physical components of docking station  10 . 
     Data storage cartridges  12  can be interfaced with docking station  10  by inserting one of cartridges  12  within receptacle  13 . Cartridges  12  may use any of a variety of data storage media including but not limited to: magnetic tape, optical discs, magneto-optic discs, magnetic discs and the like. Data storage cartridges  12  each include indications of the write-protection status. 
     Cartridges  12 A and  12 B have WORM write-protection. Permanent magnets  16 A- 16 B (magnets  16 ) on cartridge  12 A are located such that when cartridge  12 A is inserted into receptacle  13  of docking station  10 , sensors  14 A and  14 B will each detect a magnetic field. Sensor  14 A detects a magnetic field from magnet  16 A and sensor  14 B detects a magnetic field from magnet  16 B. Similarly, permanent magnet  18  on cartridge  12 B is located such that when cartridge  12 B is inserted into receptacle  13  of docking station  10 , sensors  14 A and  14 B will each detect a magnetic field from permanent magnet  18 . Cartridges  12 A and  12 B include magnets  16  and  18  that create magnetic fields detected by both of sensors  14 ; therefore, when one of cartridges  12 A and  12 B is inserted in docking station  10 , control module  11  implements WORM write-protection. Because magnets  16  and  18  are fixed, cartridges  12 A and  12 B do not include selectable write-protection and only allow WORM write-protection. 
     In contrast, cartridge  12 C has selectable write-protection. Cartridge  12 C includes a slider  20  with a single permanent magnet  22 . Slider  20  can be manually set to one of two positions to indicate the write-protection status of cartridge  12 C. One of the positions represents full write-protection; the other represents no write-protection. One of magnetic sensors  14  detects the position of the slider when cartridge  12 C is inserted into receptacle  13 . As shown in  FIG. 1 , slider  20  is set to the left: representing that cartridge  12 C currently has no write-protection. When cartridge  12 C is inserted into receptacle  13 , magnet  22  is detected by sensor  14 A, but not sensor  14 B. Control module  11  receives signals from sensors  14  and implements no write-protection for cartridge  12 C. If slider  20  is set to the right, magnet  22  is detected by sensor  14 B, but not sensor  14 A, and control module  11  implements full write-protection for cartridge  12 C. The write-protection status of cartridge  12 C can be changed repeatedly between full protection and no protection; however, cartridge  12 C cannot be set to have WORM write-protection in which both of sensors  14 A and  14 B simultaneously detect magnetic fields. 
     Cartridge  12 D has selectable write-protection provided by slider  25 . Slider  25  can be set to one of three positions, corresponding to three different statuses of write-protection: full write-protection, WORM write-protection, and no write-protection. As shown in  FIG. 1 , slider  25  is set to the middle position: representing that cartridge  12 C currently has WORM write-protection. When cartridge  12 D is inserted into receptacle  13 , magnet  26 A is detected by sensor  14 A and magnet  26 B is detected by sensor  14 B. Control module  11  receives signals from sensors  14  and implements WORM write-protection for cartridge  12 C. If slider  25  is set to the left, magnet  26 B is detected by sensor  14 A, but sensor  14 B does not detect a magnetic field. Then, control module  11  implements no write-protection for cartridge  12 D. If slider  25  is set to the left, magnet  26 A is detected by sensor  14 B, but sensor  14 A does not detect a magnetic field. Then, control module  11  implements full write-protection for cartridge  12 D. In a similar embodiment that is functionally equivalent to cartridge  12 D, magnets  26 A and  26 B on slider  25  may be replaced with a single larger magnet, like magnet  18 . 
     In some embodiments, data storage cartridges  12  may further include RF tags  24 A- 24 C (RF tags  24 ), which provide redundant write-protection status information to control module  11 . RF tags  24 A indicate that data storage cartridges  12 A and  12 B have WORM write-protection. In contrast, RF tag  24 B indicates that cartridge  12 C has a selectable write-protection status corresponding to either full write-protection or no write-protection. RF tag  24 C indicates that cartridge  12 D has a selectable write-protection status corresponding to any of full write-protection, WORM write-protection and no write-protection. In some embodiments, control module  11  can read RF tags  24  to confirm a write-protection status of an inserted cartridge  12 . RF tags  24  may simply include a unique identifier for each cartridge, and control module  11  may have to refer to a database in order to correlate that unique identifier with a write-protection status of the cartridge. 
     RF tags  24  may include additional information about cartridges  12 . For example, RF tags  24  may include information about the content of cartridges  12 , the source of such information or other information. As another example, RF tags  24  may each include a unique identifier, which can be used to correlate the cartridge  12  with a database having information about multiple cartridges  12  categorized according to unique identifiers in RF tags  24 . For example, such a database may also include information regarding the content of cartridges  12 , the source of such information or other information. In summary, the function of RF tags  24  is not limited to write-protection status indication. 
     One of cartridges  12  may also include a status bit within a media information header on data storage media of the cartridge  12 . The status bit within a media information header provides a redundant indication of the write-protection status of the cartridge  12 . Techniques for implementing a WORM status bit within a media information header are described in greater detail in the description corresponding to  FIG. 2 . 
       FIG. 2  is a table showing the function of a WORM status bit in a media information header. For example, a data storage media within one of cartridges  12  of  FIG. 1  may include a media information header with a WORM status bit as shown in  FIG. 2 . In other embodiments, the WORM status bit could be stored other places on the media, not necessarily in a header file. In different embodiments, the data storage media may comprise magnetic tape, optical discs, magneto-optic discs, magnetic discs and the like. In any case, the WORM status bit (or other such WORM information) can be stored on the media to provide redundant logical WORM information, in addition to the physical WORM information provided by the one or more magnets that interface with sensors of the docking station. 
     As shown in  FIG. 2 , the WORM status bit can be set to either “0” or “1”. “0” represents that the data storage media does not have WORM write-protection. In contrast, “1” represents that the data storage media is WORM write-protected. The WORM status bit within a media information header cannot be changed by a user, but is set during a pre-format of a data storage media during manufacture of a data storage cartridge. 
     In other embodiments, a media information header may include write-protection information in more than one bit. For example, a media information header may include two bits to represent a write-protection status of the data storage media. With two bit there are four possible combinations. One combination may represent that a cartridge has a variable write-protection status, e.g., the cartridge includes a slider that may be manually set to indicate a write-protection status. The other three combinations may be used to indicate one of three permanent write-protection statuses: full write-protection, WORM write-protection and no write-protection. Other possibilities of encoding write-protection status within a media information header are also possible. 
     Control module  11  may look to a media information header on a data storage media when a cartridge is inserted into receptacle  13  to confirm a write-protection status of the cartridge. Again, this can provide logical WORM functionality that is redundant with physical WORM functionality, e.g., functionality provided by magnets  16  in cartridge  12 A relative to sensors  14  of docking station  10 . Such physical and logical redundancy may be required to meet regulatory standards. Furthermore, physical and logical redundancy allows WORM write-protection status of a cartridge to be recognized in systems that do not include physical sensors, but support the logical read of a WORM status bit. 
       FIG. 3  is a flowchart of method  40  to determine the write-protection status of a data storage cartridge inserted into a docking station. For clarity, method  40  will be described with respect to docking station  10  from  FIG. 1 , although method  40  may be implemented in other systems as well. 
     First, one of cartridges  12  is interfaced with docking station  10 ; specifically, one of cartridges  12  is inserted within receptacle  13  ( 42 ). Control module  11  receives a signal from magnetic sensor  14 A ( 44 ). Control module  11  also receives a signal from magnetic sensor  14 B ( 46  and  48 ). 
     If neither of sensors  14  detect a magnetic field, control module  11  determines that no cartridge was detected ( 52 ). In other embodiments, for example, if control module  11  receives a separate input to determine if a cartridge has been inserted, control module  11  may perform one or more of the following actions: produce an error message, prevent access to an inserted cartridge, assume an inserted cartridge has no write-protection, assume an inserted cartridge has full write-protection, assume an inserted cartridge has WORM write-protection, look to a redundant write-protection status indicator of the cartridge to determine its write-protection status, request a user input to determine write-protection status of an inserted cartridge or perform a different action. 
     If only sensor  14 B, and not sensor  14 A, detects a magnetic field, control module  11  determines that the inserted cartridge has full write-protection. In this case, control module  11  does not allow data to be written to or erased from the inserted cartridge ( 54 ). If only sensor  14 A, and not sensor  14 B, detects a magnetic field, control module  11  determines that the inserted cartridge has no write-protection. Control module  11  then allows data to be written to and erased from the cartridge ( 56 ). When both sensors  14 A and  14 B detect a magnetic field, control module  11  determines that the inserted cartridge has WORM write-protection. Control module  11  then allows on that data can be written to, but not erased from the cartridge ( 58 ). 
     Control module  11  may look to one or more redundant write-protection status indicators of the cartridge in combination with using sensors  1  and  2  to detect magnets. For example, control module  11  may look for one of RF tags  24  ( FIG. 1 ) and/or a status bit in a data information header. Assuming the redundant write-protection status indicators of the cartridge are consistent, control module  11  would implement the corresponding write protection. In the event that the redundant write-protection status indicators are inconsistent, control module  11  may perform one or more of the following actions: produce an error message, prevent access to an inserted cartridge, assume an inserted cartridge has no write-protection, assume an inserted cartridge has full write-protection, assume an inserted cartridge has WORM write-protection, implement write-protection according to a hierarchy of the available write-protection status indicators, request a user input to determine write-protection status of an inserted cartridge or perform a different action. 
       FIG. 4  is a block diagram illustrating an automated data storage cartridge library system  70 . System  70  incorporates cartridges with different data storage media including but not limited to: magnetic tape, optical discs, magneto-optic discs, magnetic discs and the like. System  70  may comprise a tape cartridge library system that also includes a data storage disk drive  78  coupled to a tape drive emulator  79 . A system controller  75  selectively retrieves a data storage cartridge  77  from a cartridge store  81  and loads the retrieved data storage cartridge  77  into either disk drive  78  or tape drive  80 . When the drive is finished with the data storage cartridge  77 , system controller  75  retrieves the data storage cartridge  77  from the drive and returns it to the assigned storage location within cartridge store  81 . Disk drive  78  and tape drive  80  each function as docking stations for data storage cartridges. For example, each of disk drive  78  and tape drive  80  may include the features of docking station  10  described with respect to  FIG. 1  to facilitate WORM write-protection, full write-protection, or no write-protection. 
     A computing device (not shown) communicates with system controller  75  to direct operation of the data storage cartridge library system  70 . In response to an access request from the computing device, system controller  75  generates control signals to direct a robot arm  76 A and a gripper  76 B to retrieve the appropriate data storage cartridge from cartridge store  81  and insert the data storage cartridge into one of drives  78  or  80 . In response to the signals, robotic arm  76 A traverses cartridge store  81  and engages a cartridge  77  using gripper  76 B. Upon insertion of data storage cartridge  77  into one of drives  78  or  80 , the computing device can write data to, and read data from, the data storage cartridge depending on the write-protection status of the cartridge. 
     Cartridge store  81  provides a plurality of data storage cartridge storage locations. The data storage cartridges may comprise magnetic tape cartridges for use with tape drive  80  or data storage disk cartridges for use with disk drive  78 . The data storage disks may comprise blue disk media, i.e., optical disk media having a data storage capacity greater than approximately 75 GB. The data storage disk cartridges may include a plurality of data storage disk enclosed within the cartridge housing. 
     Regardless of the media type, each data storage cartridge includes a cartridge housing comprising dimensions that conform to a standard tape cartridge form factor and features for engagement by system controller  75 . In addition, the data storage cartridges may have some type of identifying information, such as a label, a bar code, or a radio frequency (RF) tag, by which the system controller  75  identifies the individual data storage cartridges. In this way, cartridges housing different types of media can be mechanically indistinguishable by system controller  75 . 
     Data storage disk drive  78  may include a tape drive emulator such that the data storage disks appear to the computing device as sequential storage devices. Specifically, tape drive emulator  79  communicates with the computing device as a conventional tape drive. For example, in response to a query from the computing device, tape drive emulator  79  may identify disk drive  78  as a conventional tape drive, such as a standard 9940 tape drive. Consequently, the drivers and other software applications executing on the computing device for accessing tape cartridges need not be modified. 
     As for the data storage disk cartridges, tape drive emulator  79  may be physically configured for use with conventional backup infrastructure, such as automated tape cartridge library system  70 . For example, disk drive  78  and tape drive emulator  79  may conform to a substantially similar dimension and form factor as conventional tape drive  80  and may be readily inserted within a drive bay of automated tape cartridge library system  70 . In this manner, data storage disk cartridges physically appear the same as magnetic tape data storage cartridges from the perspective of system controller  75 , and functionally appear the same from the perspective of the computing device. 
     A number of embodiments of the invention have been described. For example, a docking station is compatible with both WORM write-protected cartridges and cartridges allowing full or no write-protection. Nevertheless, various modifications may be made to the embodiments described above. For example, in some embodiments, a docking station may not provide backwards compatibility with current cartridges. As an example, a docking station may require cartridges with a different form factor or using different data storage medium than currently used. Accordingly, these and other embodiments are within the scope of the following claims.