[ale] problems with ssh to tape

[Geoffrey]

Greg Freemyer wrote:
> 2009/3/30 Björn Gustafsson <bg-ale at bjorng.net>:
>> Used to be that using shell redirect to a tape was unreliable and slow
>> at best, and failed at worst.  The message you get indicates to me
>> that it may be using the entire backup set size as the inferred
>> blocksize on the tape device.
>>
>> I'd try piping to dd(1) (with an appropriate block size for the tape
>> device) rather than a simple redirect.  For example:
>>
>> ssh $mach "tar -cf - $BackupThis" | dd  bs=20b  of=/dev/nst0
> 
> Those are some small blocks ;)
> 
> But I agree, tapes are very block size dependent.  When you run tar
> locally, it figures out it is talking to tape and sets the block size
> automatically.  With ssh in the middle it gets confused and messes up
> the block size.
> 
> It has been a while, but I think tar defaults to 10K blocks.  (20 * 512 bytes).
> 
> So test locally with:
> 
> tar ... | dd bs=10K of=/dev/nst0
> mt rewind
> tar -tv /dev/nst0
> 
> until you verify what bs to pass to dd.
> 
> Once you have it working, try the ssh piped to dd method.

Thanks to all, Greg's solution does appear to work on a small dataset. 
I'll be running a larger test this evening.

-- 
Until later, Geoffrey

Those who would give up essential Liberty, to purchase a little
temporary Safety, deserve neither Liberty nor Safety.
  - Benjamin Franklin