Imaging a Tape

On 03/06/2013 08:01 AM, Jonathan Katz wrote: Neither is really germane to the problem. Tar is wonderful if you're dealing with files. This is an old problem. Early tapes did not have named files--just sections of blocks separated by filemarks. Records wither corresponded to physical block sizes or some other convention, such as "a record is a group of 512-word blocks until a block shorter than 512 words is encountered". Hierarchical tape structures were possible, with each record having a record-level indicator (COBOL-style). You could similarly, have a tape where a single block could take up a sizeable part of a reel. Having spent a couple of years maintaining tape software, I can say that there were a bewildering number of tape conventions and schemes. Software to deal with differences between systems and vendors with regards to tape was an important part of the mainframe culture. A tape imaging scheme that doesn't preserve the differences is rather short-sighted. dd does not preserve blocking. --Chuck