Method and apparatus for improving inter-block gap length tolerance and locate accuracy for write appends

A tape drive for writing data at an intended append location of a tape mounted therein, comprising:

• a read/write head;
• a dataflow mechanism for detecting End of Block markers located at the end of data blocks stored on said tape;
• means for moving the tape relative to said read/write head;
• means for storing tach counts corresponding to End of Block markers located on said tape;
• means for positioning said tape such that said read/write head is proximate to a tape position at least three data blocks upstream of said intended write append location;
• and
• means for advancing said tape toward said intended write append location, simultaneously comparing said stored tach counts with a current dataflow position indication corresponding to said End of Block markers for said data blocks only while advancing said tape toward said intended write append location and using said comparison to adjust said tape position relative to said read/write head such that said write append occurs at said intended write append location.

A method for appending data to a tape medium, the method comprising the steps of:

• receiving a command to write a first data block to said tape medium at a write append point;
• determining reference IBG for said first data block;
• determining and storing tach count corresponding to an End of Block mark for a second data block immediately upstream of said reference IBG:
• positioning said tape medium at a third data block immediately upstream of a second IBG located immediately upstream of said second data block;
• acquiring said second data block;
• reading said second data block;
• detecting an End of Block mark at the termination of said second data block;
• determining if said stored tach count is acceptably close to a current tach count;
• if said current and said stored tach counts are acceptably close, adjusting said write append point by the difference between said current and said stored tach count.

A method for performing a write append operation to a tape medium mounted in a tape device having a read/write head, said method comprising the steps of:

• positioning said tape medium such that said read/write head is proximate to a tape position at least three data blocks upstream of an intended write append location;
• advancing said tape medium toward said intended write append location while simultaneously storing at least one tach count corresponding to End of Block positions for said data blocks;
• stopping said tape medium after storing said at least one tach count;
• backhitching said tape medium such that said read/write head is proximate to a tape position at least three data blocks upstream of said intended write append location;
• advancing said tape medium toward said intended write location, simultaneously comparing said at least one said stored tach count with a current dataflow position indication corresponding to said End of Block markers for said data blocks only while advancing said tape medium toward said intended write location and using said comparison to adjust said tape position relative to said read/write head such that said write append occurs at said intended write append location.