Subject: Re: what have changed in st driver?
To: Wojciech Puchar <>
From: Paul Ripke <>
List: current-users
Date: 12/28/2003 11:34:08
On Sunday, Dec 28, 2003, at 07:11 Australia/Sydney, Wojciech Puchar 

> 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 
            integer number of bytes per write to the archive file.  The
            blocksize must be a multiple of 512 bytes with a maximum of 
            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. 
                    chives with a blocking factor larger 63 violate the 
                    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
I love deadlines. I like the whooshing sound they make as they fly by.
-- Douglas Adams