Alan Stern wrote:
On Mon, 6 Feb 2006, [EMAIL PROTECTED] wrote:
Hi everybody,
I recently bought 2 large USB disk for doing backups. New disks are
approx. 400 GB in large, usb 2.0. My backup program (Bacula 1.36.3)
sucessfully writes to one of that disks and everything goes well. I
bought usb disks for quick solution for doing backups as my streamer
eaten another tape :? , and I would be happy to replace it with usb
disks for convienience, reliability and - price.
The problem occurs when I need to copy a bigger file from one disk to
another: no matter if it is normal SCSI disk in the computer or second
USB drive. While copying bacula archive (a single file, which is 8GB in
large now and will grow up to 50GB) afer some time (300-900MB) copying
process slows down until it stops, slowly restart and continue copying.
Because of that slow average speed of copying to and from usb 2.0 is
about 2-3 MB/s only. While this process goes I can see in logs:
[kernel] usb 1-2: reset high speed USB device using ehci_hcd and address 5
This line repeats continously until I finish copying. After starting
copying again, I still can see the message, but now since the very
beginning. Unregistering the device and restarting the backup machine
solves a problem until next copy.
I've checked md5 sums of copies and they are correct (uf!), I can also
restore backups. I assume the problem lies somewhere in kernel, because
it happens also on another computer.
Not necessarily. The problem could lie in the drive or in the USB cables.
Be sure to check or replace them, and don't forget the cables inside the
computer case (if you're using one of the front-side USB ports that isn't
directly adjacent to the motherboard).
I have to say that I really need a solution, because I feel unsafe to
perform backups to a device which is not managed correctly by my kernel.
Maybe I miss something in the kernel configuration or I need another
solution? The filesystem I use is ext3.
To get more information, you should turn on the USB Mass Storage verbose
debugging option in the kernel configuration (CONFIG_USB_STORAGE_DEBUG)
and rebuild the usb-storage driver.
For testing, use only one of the USB drives; unplug the other one. The
usb-storage debugging option will generate a _lot_ of debugging messages,
so make sure your /etc/syslog.conf is set up not to store debug-level
messages from the kernel. Then go ahead and start writing a large amount
of data to the drive. When you see those resets start to occur, run dmesg
and post a copy of the output.
Alan Stern
Am I really getting insane? I recompiled kernel (and upgraded to
2.6.15-gentoo-r3) but that didn't help either. I've tested cables, and
so on. Still nothing, still have errors and the slow.
Debug messages say the same things as about 4 years ago when I was
happily checking out first usb mass storage driver in kernel (then I was
trying home-made usb disk made with Seagate 4GB and interface based on
Cypress chip, but instead of working I had my machine hung).
During my visit in servers' room I did nothing but switched USB cables
each other, and that partialy helped - I successfully managed to copy
57GB of data between 2 USB disk with only 11 such errors. Md5 sums are
correct.
But by my mistake (I've got Big Blue machine which can't boot from scsi
but only floppy) I booted to previous kernel, so the solution was to
switch USB cables each other? I thought I'm experienced in hardware,
but I'm surprised.
Neverthless I still think that the issue of poorly written usb driver in
the kernel should be considered. I use about 7 of IBM 206 and 226
machines and on every Linux one I found the same problem using all kind
(long, short, old, new, expensive and cheap) of cables. Under Windows
there is no such problem at all!
Maybe usb driver needs some throttling when a cheap device does not meet
all specific to USB requirements? I can understand that resetting high
speed device performed by kernel could be perceived as a solution but it
is way too rough for me.
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