Patent Publication Number: US-2007115579-A1

Title: Method to test a tape drive

Description:
FIELD OF THE INVENTION  
      Applicant&#39;s invention relates to an apparatus and method to test a tape drive.  
     BACKGROUND OF THE INVENTION  
      Automated media storage libraries are known for providing cost effective access to large quantities of stored media. Generally, media storage libraries include a large number of storage slots on which are stored portable data storage media. The typical portable data storage media comprises a magnetic tape. One (or more) accessors typically accesses a tape cassette from a storage slot and delivers that cassette to a tape drive for reading and/or writing data. Suitable electronics operate the accessor(s) and operate the tape drive to provide information to, and/or to receive information from, an attached on-line host computer system.  
      What is needed is a method to test a tape drive and its mid-tape recovery abilities, where that tape drive comprises a newly-manufactured unit (as a standalone unit), and/or when that tape drive is installed in an automated media library.  
     SUMMARY OF THE INVENTION  
      Applicant&#39;s invention comprises a method to test a tape drive and its mid-tape recovery abilities. Applicant&#39;s method provides a tape drive, and disposes a magnetic tape in that tape drive, wherein the magnetic tape comprises a physical beginning of tape (“PBOT”) and a physical end of tape (“PEOT”). The method writes data from the PBOT to the PEOT, rewinds the tape to the PBOT, and moves the tape from said PBOT toward the PEOT. While the magnetic tape is still moving, the method resets the tape drive. The method then validates the tape drive&#39;s ability to recover the tape to a ready position and the data written to the magnetic tape. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The invention will be better understood from a reading of the following detailed description taken in conjunction with the drawings in which like reference designators are used to designate like elements, and in which:  
       FIG. 1  is a perspective view of a first embodiment of Applicant&#39;s data storage and retrieval system;  
       FIG. 2  is a perspective view of a second embodiment of Applicant&#39;s data storage and retrieval system;  
       FIG. 3  is a flow chart summarizing the steps of Applicant&#39;s method. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Referring to the illustrations, like numerals correspond to like parts depicted in the figures. The invention will be described as embodied in an automated data storage and retrieval subsystem for use in a data processing environment. The following description of Applicant&#39;s method to test a tape drive is not meant, however, to limit Applicant&#39;s invention to either data storage and retrieval systems, or to data processing applications, as the invention herein can be applied to testing tape drives in general.  
      Referring now to  FIG. 1 , automated data storage and retrieval system  100  is shown having a first wall of storage slots  102  and a second wall of storage slots  104 . Portable cassettes each comprising a magnetic tape are individually stored in these storage slots.  
      Applicant&#39;s automated data storage and retrieval system includes one or more accessors, such as accessors  110  and  120 . An accessor is a robotic device which accesses portable cassettes from first storage wall  102  or second storage wall  104 , transports that accessed cassette to data tape drives  130  or  140  for reading and/or writing data thereon, and returns the media to a proper storage slot.  
      Library controller  150  comprises a processor  152  and instructions  154  to operate system  100 . Power component  160  comprises one or more power supply units which supply power to, inter alia, tape drives  130  and  140 .  
       FIG. 2  shows system  200  which comprises another embodiment of Applicant&#39;s data storage and retrieval system. System  200  includes first storage wall  202  and second storage wall  204 . Storage walls  202  and  204  each include a plurality of storage elements in which can be stored a plurality of portable cassettes  220  each comprising a magnetic tape. System  200  includes tape drive  230 . System  200  also includes at least one robotic accessor  210  for transporting a designated portable cassette  220  between a storage slot disposed in first wall  202  or second wall  204  and tape drive  230 . Power component  240  supplies power to, inter alia, tape drive  230 .  
      Applicant&#39;s invention comprises a method to test a tape drive, such as tape drive  130  ( FIG. 1 ), and/or tape drive  140  ( FIG. 1 ), and/or tape drive  230  ( FIG. 2 ), disposed in an information storage and retrieval system, such as for example system  100  ( FIG. 1 ) or system  200  ( FIG. 2 ). In certain embodiments, Applicant&#39;s method comprises testing such tape drive on a regular, on-going basis. In addition, Applicant&#39;s method can be used to test newly-manufactured tape drives before those drives are installed in an information storage and retrieval system, such as system  100  or system  200 .  
      Applicant&#39;s method tests all the mechanical and electrical functions of such an installed or newly-manufactured tape drive. All data paths to the tape drive are tested. The drive response to one or more LOCATE commands is tested. Servo sensors, tape pickup devices, tape threading mechanisms, are tested. As the tape head disposed in the tape drive is caused to move up and down, various stepper motors disposed in the tape drive are tested.  
      In addition, Applicant&#39;s method power cycles that drive to test the drive&#39;s “mid-tape recovery” function, wherein the tape drive is subjected to an unexpected power loss while the tape drive is actively moving a magnetic tape storage medium. As a result of such an unexpected power loss, the tape drive should slowly cause the moving tape to stop moving without damaging the tape or corrupting the data written thereto.  
      Applicant&#39;s method first writes data to a magnetic tape disposed in the tape drive under test, after performing a plurality of test functions, Applicant&#39;s method attempts to validate that data. If the data can be validated, then the tape drive functions, including the mid-tape recovery function, have been successfully tested.  
       FIG. 3  summarizes the steps of Applicant&#39;s method. Referring now to  FIG. 3 , in step  305  Applicant&#39;s method provides a tape drive, such as for example tape drive  130  ( FIG. 1 ),  140  ( FIG. 1 ),  230  ( FIG. 2 ). In certain embodiments, the tape drive of step  305  comprises a newly-manufactured tape drive that has not been installed in a data storage library such as system  100  ( FIG. 1 ) or system  200  ( FIG. 2 ).  
      In certain embodiments, step  305  further comprises providing test data  156  ( FIG. 1 ). In the illustrated embodiment of  FIG. 1 , test data  156  is stored in library controller  150 .  
      In step  310 , Applicant&#39;s method disposes a magnetic tape data storage medium (“magnetic tape”) in the tape drive of step  305 , wherein that magnetic tape comprises a physical beginning of tape (“PBOT”) and a physical end of tape (“PEOT”). In certain embodiments, the magnetic tape of step  310  is disposed within a portable cassette housing. In certain embodiments, step  310  is performed by a robotic accessor, such as for example accessor  110  ( FIG. 1 ), accessor  120  ( FIG. 1 ), or accessor  210  ( FIG. 2 ). In other embodiments, step  310  is performed manually.  
      In step  315 , Applicant&#39;s method writes, using the tape drive of step  305 , data to the magnetic tape of step  310 . In certain embodiments, step  315  further comprises writing data from the PBOT to the PEOT. In certain embodiments, step  315  comprises writing the test data of step  305 . In certain embodiments, Applicant&#39;s method transitions from step  315  to step  325 .  
      In other embodiments, Applicant&#39;s method transitions from step  315  to step  320  wherein in certain embodiments the method determines the number blocks of data written in step  315  to the magnetic tape of step  310  using the tape drive of step  305 . In certain embodiments, step  320  comprises determining a first checksum for the data written in step  315 . In certain embodiments, step  320  comprises determining first cyclic redundancy check (“CRC”) information for the data written in step  315 . In certain embodiments, step  320  comprises determining first longitudinal redundancy check (“LRC”) information for the data written in step  315 . In certain embodiments, step  320  is performed by a controller, such as controller  150  ( FIG. 1 ), disposed in a data storage and retrieval system, such as system  100  ( FIG. 1 ), comprising the tape drive, such as tape drive  130  ( FIG. 1 ) or tape drive  140  ( FIG. 1 ).  
      Applicant&#39;s method transitions from step  320  to step  325 , wherein the method rewinds the magnetic tape from the PEOT to the PBOT using the tape drive of step  305 . In certain embodiments, Applicant&#39;s method transitions from step  325  to step  340 .  
      In other embodiments, Applicant&#39;s method transitions from step  325  to step  330  wherein the method issues a LOCATE TO END OF DATA command, and wherein the method determines a first time interval comprising the time required to move the magnetic tape from the PBOT to the PEOT. In certain embodiments, step  330  is performed by a controller, such as controller  150  ( FIG. 1 ), disposed in a data storage and retrieval system, such as system  100  ( FIG. 1 ), comprising the tape drive, such as tape drive  130  ( FIG. 1 ) or tape drive  140  ( FIG. 1 ). Applicant&#39;s method transitions from step  330  to step  335  wherein the method rewinds the magnetic tape from the PEOT to the PBOT using the tape drive of step  305 .  
      Applicant&#39;s method transitions from step  335  to step  340  wherein the method moves the magnetic tape from the PBOT toward the PEOT. In certain embodiments, Applicant&#39;s method transitions from step  340  to step  350 . In certain embodiments, step  340  comprises issuing a command that can return good status prior to the command completing, thereby returning control of the tape drive to a library controller before completing these commands, which is the objective. In certain embodiments, step  340  comprises issuing a READ command of step  345 . In certain embodiments, step  340  comprises issuing a WRITE command of step  345 . In certain embodiments, step  340  comprises issuing a WRITE FILEMARK command of step  345 . In certain embodiments, step  340  comprises issuing a ERASE command of step  345 . In certain embodiments, step  340  comprises issuing a LOCATE command of step  345 .  
      In certain embodiments, step  340  comprises issuing a LOCATE TO END OF DATA WITH IMMEDIATE BIT ON command of step  345 . Such a LOCATE TO END OF DATA WITH IMMEDIATE BIT ON command returns a good status immediately, and prior to completing the command, thereby returning control of the tape drive to a library controller before completing the LOCATE command.  
      Applicant&#39;s method transitions from step  345  to step  350  wherein the method resets the tape drive while the magnetic tape is moving from the PBOT to the PEOT. Such a tape drive reset mimics an unexpected power loss to the tape drive while that drive is moving the magnetic tape. As described above, the tape drive should automatically execute a graceful braking algorithm on the tape media whereunder the movement of the magnetic tape is slowly stopped without damaging the magnetic tape or corrupting the data written thereto. To ensure that the magnetic tape is still moving at the time of tape drive reset, in certain embodiments step  350  comprises determining a second time interval commencing from the implementation of step  340  and ending with the tape drive reset of step  350 , such that the second time interval is less than the first time interval of step  330 . In certain embodiments, step  350  is performed by a controller, such as controller  150  ( FIG. 1 ), disposed in a data storage and retrieval system, such as system  100  ( FIG. 1 ), comprising the tape drive, such as tape drive  130  ( FIG. 1 ) or tape drive  140  ( FIG. 1 ). In certain embodiments, Applicant&#39;s method transitions from step  350  to step  370 .  
      In certain embodiments, step  350  comprises step  355  wherein the reset of step  350  comprises interrupting the power from a power source, such as power source  160  ( FIG. 1 ), to the tape drive. Applicant&#39;s method transitions from step  355  to step  360  wherein the method restores the power to the tape drive. In certain embodiments, steps  355  and  360  are performed by a controller, such as controller  150  ( FIG. 1 ), disposed in a data storage and retrieval system, such as system  100  ( FIG. 1 ), comprising the tape drive, such as tape drive  130  ( FIG. 1 ) or tape drive  140  ( FIG. 1 ). Applicant&#39;s method transitions from step  360  to step  370 .  
      In certain embodiments, step  350  comprises step  365  wherein the method issues a SEND DIAG command for Self-Test to the tape drive causing the tape drive to reset. In certain embodiments, step  365  is performed by a controller, such as controller  150  ( FIG. 1 ), disposed in a data storage and retrieval system, such as system  100  ( FIG. 1 ), comprising the tape drive, such as tape drive  130  ( FIG. 1 ) or tape drive  140  ( FIG. 1 ). Applicant&#39;s method transitions from step  365  to step  370 .  
      In step  370 , Applicant&#39;s method waits for the tape drive to reestablish communication. In certain embodiments, step  370  comprises waiting for the tape drive to reestablish communication with a controller, such as controller  150  ( FIG. 1 ), disposed in a data storage and retrieval system, such as system  100  ( FIG. 1 ), comprising the tape drive, such as tape drive  130  ( FIG. 1 ) or tape drive  140  ( FIG. 1 ).  
      Applicant&#39;s method transitions from step  370  to step  375  wherein the method rewinds the magnetic tape to the PBOT. In certain embodiments, step  375  comprises part of the tape drive&#39;s mid-tape recovery algorithm.  
      Applicant&#39;s method transitions from step  375  to step  390  wherein the method validates the test data written to the tape in step  315 . In certain embodiments, step  390  comprises step  380  wherein the method determines a second checksum for the data written to the magnetic tape. In certain embodiments, step  390  comprises step  380  wherein the method determines second CRC information for the data written to the magnetic tape. In certain embodiments, step  390  comprises step  380  wherein the method determines a second LRC information for the data written to the magnetic tape. In certain embodiments, step  380  is performed by a controller, such as controller  150  ( FIG. 1 ), disposed in a data storage and retrieval system, such as system  100  ( FIG. 1 ), comprising the tape drive, such as tape drive  130  ( FIG. 1 ) or tape drive  140  ( FIG. 1 ). Applicant&#39;s method transitions from step  365  to step  370 .  
      Applicant&#39;s method transitions from step  380  to step  385  wherein in certain embodiments, Applicant&#39;s method compares a first checksum of step  320  with a second checksum of step  380  to validate the data written to the magnetic tape. In certain embodiments, step  385  comprises comparing first CRC information of step  320  with second CRC information of step  380  to validate the data written to the magnetic tape. In certain embodiments, step  385  comprises comparing first LRC information of step  320  with second LRC information of step  380  to validate the data written to the magnetic tape. In certain embodiments, step  385  is performed by a controller, such as controller  150  ( FIG. 1 ), disposed in a data storage and retrieval system, such as system  100  ( FIG. 1 ), comprising the tape drive, such as tape drive  130  ( FIG. 1 ) or tape drive  140  ( FIG. 1 ). Applicant&#39;s method transitions from step  365  to step  370 .  
      If Applicant&#39;s method can validate the data written to the magnetic tape in step  390 , then the tape drive of step  305  has passed Applicant&#39;s test method of  FIG. 3 . On the other hand, if Applicant&#39;s method cannot validate the data written to the magnetic tape in step  390 , then the tape drive of step  305  did not pass Applicant&#39;s test method of  FIG. 3 .  
      In certain embodiments, the individual steps of  FIG. 3  can be combined, reordered, or eliminated. For example, in certain embodiments, Applicant&#39;s method comprises steps  305 ,  310 ,  315 ,  325 ,  340 ,  350 ,  370 , and  390 . In other embodiments, Applicant&#39;s method comprises steps  305 ,  310 ,  315 ,  325 ,  330 ,  335 ,  340 ,  350 ,  370 , and  390 . In other embodiments, Applicant&#39;s method comprises steps  305 ,  310 ,  315 ,  325 ,  330 ,  335 ,  340 ,  345 ,  350 ,  370 , and  390 . In other embodiments, Applicant&#39;s method comprises steps  305 ,  310 ,  315 ,  325 ,  330 ,  335 ,  340 ,  345 ,  350 ,  365 ,  370 , and  390 . In other embodiments, Applicant&#39;s method comprises steps  305 ,  310 ,  315 ,  325 ,  330 ,  335 ,  340 ,  345 ,  350 ,  355 ,  360 ,  370 , and  390 . In other embodiments, Applicant&#39;s method comprises steps  305 ,  310 ,  315 ,  325 ,  330 ,  335 ,  340 ,  345 ,  350 ,  365 ,  370 ,  380 ,  385 , and  390 .  
      Applicant&#39;s invention includes instructions residing in a computer program product, where those instructions are executed by a computer external to, or internal to, system  100  ( FIG. 1 ) and/or system  200  ( FIG. 2 ), to perform steps one or more of steps  310 ,  315 ,  320 ,  325 ,  330 ,  335 ,  340 ,  345 ,  350 ,  355 ,  360 ,  365 ,  370 ,  380 ,  385 , and/or  390 , recited in  FIG. 3 . Such instructions may be encoded in an information storage medium comprising, for example, a magnetic information storage medium, an optical information storage medium, an electronic information storage medium, and the like. By “electronic storage media,” Applicants mean, for example, a device such as a PROM, EPROM, EEPROM, Flash PROM, compactflash, smartmedia, and the like.  
      While the preferred embodiments of the present invention have been illustrated in detail, it should be apparent that modifications and adaptations to those embodiments may occur to one skilled in the art without departing from the scope of the present invention as set forth in the following claims.