LTO-2 tape device is very slow?

[Ed K.]

On Tue, 14 Dec 2004, Tom Haws wrote:

> I'm having problems adding an Exabyte Magnum LTO-2 tape device to my RHL 9 
> machine.  I know that's a different OS, so thius question should go in the 
> shrike lists, but it's close enough to Fedora that I thought I might get some 
> answers here, and the shrike lists are just about dead now.  Red Hat 
> announced the end of RHL 9 2 months after I installed a production server on 
> it...  arrrghh...
>
> Anyway, after I add the device, it shows up fine in /proc/scsi/sci, and I can 
> write to it, but it is extremely slow.  I got about 30MB written in 5 
> minutes!  Has anyone else had any experience with LTO-2 devices on Fedora or 
> RHL 9 systems, and is there anything I can do to recreate device files or 
> anything to speed it up?
>
> Also, do you know if I do a "mknod -m 666 /dev/st0 c 9 0" with the tape drive 
> hooked up, does it do anything different than if there wasn't one installed? 
> Like read the status bits on the drive to tell what it's capabilities are?
>

Tom,

I have a similar problem on a DLT-1 on a FC1 computer, and had problems 
with speed until I found the proper way to write to the tape. Here are the 
commands to prime the tape:

modprobe st buffer_kbs=1024 max_buffers=128 max_sg_segs=128 
blocking_open=1
mt setblk $[64*1024]

#test
tar -cf - .|mbuffer -s $[64*1024]  > /dev/tape
mbuffer -s $[64*1024] < /dev/tape > /dev/null

You can find mbuffer at:
http://directory.fsf.org/All_Packages_in_Directory/mbuffer.html

ed