[ale] writing to tape

[Greg Freemyer]

2010/2/2 Björn Gustafsson <bg-ale at bjorng.net>:
> On Mon, Feb 1, 2010 at 10:31 AM, Geoffrey <lists at serioustechnology.com> wrote:
>> Greg Freemyer wrote:
>>> What's your command line including pipes.
>>
>> ssh servername "tar -cf - $BackupThis" | dd bs=10k of=/dev/nst0
>
> I don't know if it works with GNU tar, but you might want to try the
> -B switch and/or to set `-b 20' to explicitly match the dd blocksize.
> (20 should be the default though.)
>
> After quickly checking the GNU tar manpage, it seems to indicate that
> -B only works for reads, but it might be worth a try anyway.
>
> --
> Björn Gustafsson

tar is not the problem.  Its whatever the interconnect is between the machines.

It is not keeping up with the tape drive so dd is stalling out on the
input from the comm channel and creating partial blocks on its output.
 dd is just not really a good tool for this use case.

I've come across similar issues in the past.  My solution was to us
mbuffer as I said in a previous email.

I think this is what I used <http://www.maier-komor.de/mbuffer.html>
but it was years ago.  Back then it was not really well supported and
I had to patch in some fixes..  To my surprise it is now in the
opensuse distro, so maybe others as well.

Greg
-- 
Greg Freemyer
Head of EDD Tape Extraction and Processing team
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