Some tape files may use different blocking size. If we try to read the file whose blocking size is different from their actual written block size.
To prevent this use a blocking
factor of 1 can be used, although performance may be reduced somewhat. Use with -b 1 on tar file
More informations are given over tar man page on b option as,
----------------
Use the next arg argument as the blocking factor for archive
records. The default is 20; the maximum is at least 20.
However, if the f - modifier is used to specify standard
input, the default blocking factor is 1.
The blocking factor is determined automatically when reading
nine-track tapes (key letters x and t). On nine-track
tapes, the physical tape record length is the same as the
block size. The block size is defined as the logical record
size times the blocking factor (number of logical records
per block).
The blocking factor must be specified when reading flexible
disks and cartridge tapes if they were written with a
blocking factor other than the default.
If a tar file is read using a blocking factor not equal to
the one used when the file was written, an error may occur
at the end of the file but there may or may not be an actual
error in the read. To prevent this problem, a blocking
factor of 1 can be used, although performance may be reduced
somewhat.
tar writes logical records of 512 bytes, independent of how
logical records may be defined elsewhere by other programs
(such as variable-length records (lines) within an ASCII
text file).
Easy to suggest when don't know about the problem!
