Best tar blocking factor for HP DDS tape drive ?

Best tar blocking factor for HP DDS tape drive ?

Post by WONG SAI-KE » Fri, 14 Sep 2001 23:12:32

There is blocking-factor option for the tar cmd.  It seems the tar write
to the tape drive for every blocking-factor (default is 20) X 512 bytes.
And the tape drive write and skip to next block even if the data size
is less than tape drive's block size.

Since DDS is using rotary head, I guess the block size of such tape
is the data stored during half round of the head turning.  Which may
be 10K bytes to 200K bytes.  Anyone knows the block size of DDS-1, 2, 3
such that we can tune to best blocking-factor when using tar ?

Or the efficiency was optimized internally by the drive (since it also
perform compression) and the user doesn't need to care about it ?
Then, why you have to match the blocking-factor during create and extract ?

Thanks in advance.