> under NetBSD 1.6R (unfortunately I don't have a tape drive attached to
> my 1.6ZG system):
>
> ksh$ dd if=/dev/zero of=/dev/rst0 bs=64k count=160
> 160+0 records in
> 160+0 records out
> 10485760 bytes transferred in 51.613 secs (203161 bytes/sec)
>
> I assume you have the hardware blocksize set to 0 to force variable
> blocksizes? You should see this in the output from "mt status".


yes i did.
>
> >> To: Wojciech Puchar <wojtek@tensor.3miasto.net>
> >> Cc: current-users@NetBSD.org
> >> Subject: Re: what have changed in st driver?
> >>
> >>
> >> On Sunday, Dec 28, 2003, at 07:11 Australia/Sydney, Wojciech Puchar
> >> wrote:
> >>
> >>> i've been able to use 32K blocks on exactly that tape drive in 1.5.*
> >>>
> >>> now:
> >>>
> >>> root@serwer# tar -b64 -cvf /dev/rst0 /bin /sbin
> >>> tar: Write block size of 32768 too large, maximum is: 32256
> >>
> >> I think you'll find this is due to the switch to tar-is-pax. From the
> >> pax(1) manpage:
> >>
> >>       -b blocksize
> >>             When writing an archive, block the output at a positive
> >> decimal
> >>             integer number of bytes per write to the archive file.
> >> The
> >>             blocksize must be a multiple of 512 bytes with a maximum
> >> of
> >> 32256
> >>             bytes.  A blocksize can end...
> >>
> >> However, from the tar(1) manpage:
> >>
> >>       -b blocking factor, --block-size blocking factor
> >>                     Set blocking factor to use for the archive.  tar
> >> uses 512
> >>                     byte blocks.  The default is 20, the maximum is
> >> 126.
> >>   Ar-
> >>                     chives with a blocking factor larger 63 violate
> >> the
> >> POSIX
> >>                     standard and will not be portable to all systems.
> >>
> >> Looks like the later needs updating. BTW, this is current as of around
> >> 2003-12-08, haven't looked for more recent changes.
> >>
> >> If you want larger, non-POSIX blocking factors, you can always install
> >> another tar variant from pkgsrc.
> >>
> >>> the drive is:
> >>> st0 at scsibus0 target 6 lun 0: <ARCHIVE, IBM4326NP/RP  !D, 04BK>
> >>> tape
> >>> removable
> >>> st0: drive empty
> >>> st0: sync (200.00ns offset 15), 8-bit (5.000MB/s) transfers
> >>
> >
> --
> Paul Ripke
> Unix/OpenVMS/TSM/DBA
> I love deadlines. I like the whooshing sound they make as they fly by.
> -- Douglas Adams
>