Efficient multichannel data format using variable-length headers

A system for writing data using variable-length headerized CWI-4 sets, the system comprising:

• a controller;
• and
• logic, wherein the logic is at least one of:
• integrated with the controller as hardware instructions, and executable by the controller, the logic being configured to cause the controller to:
• cause performance of a first write of a data set to a first write section of a magnetic medium, the data set comprising a plurality of sub data sets, each sub data set comprising a data array organized in rows and columns, each row of the data array comprising four interleaved C1 codewords (a CWI-4), wherein a first portion of the data set is stored as CWI-4 sets to the first write section of the magnetic medium with first headers, a CWI-4 set comprising a fixed number of M concurrently written CWI-4s having M corresponding first headers;
• and
• cause performance of a rewrite of at least some of the data set as rewritten CWI-4 sets to a rewrite section of the magnetic medium, wherein each rewritten CWI-4 set is stored to the rewrite section of the magnetic medium as M rewritten CWI-4s having M corresponding rewrite headers,
• wherein the rewritten CWI-4 sets are determined based on errors being detected in CWI-4s stored in the first write section of the magnetic medium, and
• wherein a length of any one of the rewrite headers is greater than a length of any one of the first headers.