On Fri, Jun 12, 2009 at 11:27 AM, Jean-Francois
Malouin<malin AT bic.mni.mcgill DOT ca> wrote:
> I can't get better than ~60MiBs to LTO4 tape when using amtapetype.
> I tried 32k 1024k and 2048k, with and without hw compression enabled.
> Any hints? I've added some info below. I can provide more upon request.

60 MiB/s is certainly capable of hitting a number of hardware
bottlenecks - RAM, SCSI, PCI bus, even CPU when generating random
data.  You may want to try a simpler test with just 'dd' from e.g,
/dev/zero and /dev/urandom.

> Note that tapeinfo reports hw compression off but amtapetype says it
> on. The changer web interface also tells me that the drive has
> hardware compression off too. Puzzling.

amtapetype detects compression by noting that it can fit more data on
tape when using a fixed byte pattern than when writing pseudo-random
data.

Dustin

-- 
Open Source Storage Engineer
http://www.zmanda.com