On Tue, Jan 05, 2010 at 04:55:51PM -0500, John Drescher wrote:

> >> I'm not seeing anywhere close to 60M/s ( < 30 ).  I think I just fixed
> >> that.  I increased the block size to 1M, and that seemed to really
> >> increase the throughput, in the test I just did.  I will see tomorrow,
> >> when it all runs.
> >
> > Yes, if you aren't already, whenever writing to tape you should almost
> > without exception (and certainly on any modern tape drive) be using the
> > largest block size that btape says your drive supports.
> 
> I tried to do that years ago but I believe this made all tapes that
> were already written to unreadable (and I now have 80) so I gave this
> up. With my 5+ year old dual processor Opteron 248 server I get 25MB/s
> to 45MB/s despools (which measures the actual tape rate) for my LTO2
> drives. The reason for the wide range seems to be compression.

Can anybody confirm or rebute this for 2.2.x? I'm currently fiddling
with Maximum Block Size and a shiny new tape. It looks like 1M is too
much for my tape drive, but 512K seems to work and it's making a huge
difference: btape fill reports > 60 MB/s right at the beginning, then
drops to abour 52 MB/s.

Thanks,

Tino.

-- 
"What we nourish flourishes." - "Was wir nähren erblüht."

www.lichtkreis-chemnitz.de
www.tisc.de

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