Ed K. wrote:
Thanks for your suggestions, Ed. I didn't actually try your solution above, but thanks to your reply and C. Linus Hick's reply, it got me thinking about blocksize, and that's what proved to be the solution.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.
Anyway, after I add the device, it shows up fine in /proc/scsi/scsi, 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?
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
I had originally looked at Exabyte's ltoTool and libTool as per C. Linus Hick's reply, but at first glance thought they were just for flashing the firmware. Get them here: http://www.exabyte.com/support/online/downloads/downloads.cfm?prod_id=581
Actually, libTool is pretty cool- like mtx, you can move media from slot to drive etc. And ltoTool offers a test function. It wrote and read back 4GB in only a few minutes using /dev/st0, so I knew my tape device was ok.
Then I noticed that mt reports that the tape block size is 32768 bytes:
mt -t /dev/nst0 status SCSI 2 tape drive: File number=18, block number=0, partition=0. Tape block size 32768 bytes. Density code 0x42 (no translation). Soft error count since last status=0 General status bits on (81010000): EOF ONLINE IM_REP_EN
When I used tar and dump with a "-b 32" or "-b 64" to manually set the block size, it just flew. My transfer rate went from 10kb/s with the default 10k block size, to 11000kb/s with either 32k or 64k block sizes. Much more like the performance I was expecting...
This is good enough to get me using the device right now, but I'd still like to try the mbuffer solution above. I would try "star" as suggested by J. Epperson, but it does not allow a single file to span tapes yet, and I need that.
Thanks, and keep posting! -Tom
-- _______________________________________________________________________ Tom Haws Manager, Systems Administration trh@xxxxxxxxxxxxx Timberline Forest Inventory Consultants Tel: (250) 562-2628 1579 9th Ave, Prince George, B.C. Canada V2L 3R8 Fax: (250) 562-6942 http://www.timberline.ca _______________________________________________________________________
