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Reading from Tape

Data is read from tape most commonly via a command named jget.  The requirements for using this tool

  1. a valid scientific computing
    certificate as described in "Getting
  2. access to /site/bin/jget on a
    supported machine.

Files may also be read from
tape via other special-purpose tools documented elsewhere. 
Regardless of the the way that read requests are generated, the
ultimate process that jasmine uses to service those requests is as

  1. For each source file in the
    stub filesystem, the request will fail if any of the following
    conditions pertain:
  • the file does not exist.
  • For each destination file, the request will fail if any of the following conditions pertain:
    • destination file already exists,
    • another request already
      exists to write the same destination (either same location on network filesystem, or same local path on same host machine),
    • the user does not have
      permission to write the destination file.
  • Once a request has been
    created successfully, it will be assigned a unique identifier. 
    Each job in the request will also be given its own unique identifier
    and assigned an initial state of Pending
    The meaning of job states for read requests is as
    • Pending - the
      job is waiting to be
    • Staging - the tape is being prepared for reading the file
    • Staged - the tape is ready to read the file
    • Running -
      the file is being read from tape and written to its destination
    • Done - the file was
      successfully read from tape and written to its destination
    • Cancelled - the job was
    • Failed - an error
      prevented the file from going from tape to its detination
  • When the jasmine scheduler
    determines it's time to start processing a file, a data mover service
    will either contact the client via socket to stream the file over the
    network or, if possible, copy the file directly from tape to its destination on a network filesystem.
  • If a
    non-fatal error occurs at any point in the processing of a file, its
    state will automatically be reset for a future retry.  The jget client will display each job's state as it is