Greetings,

I'm looking for some insight into a performance issue with an external hard drive--I'm imaging the internal hard disk to it, and something is telling me that I should be able to expect a bit more than abysmal 800,000 bytes/sec transfer rates--this image of a 40Gig drive has been running for over 13 hours now!).

I'm working with a year-or-so old HP Compaq NX9010 laptop that I've booted to a Knoppix CD which runs a 2.4.27 kernel. In Knoppix, I'm in the process of imaging the internal hard disk (which has a broken windows installation i'm hoping to fix) out to a 250G USB2.0 external drive--a Maxtor OneTouch. The laptop specs USB 2.0 and this new external hard disk does as well. I'm using the usb cable that came with the external disk. I did have to repartition the external disk splitting it into FAT and ext2 partitions (since FAT32 wouldn't come close to supporting the file size my images would create).

The command I started 13 hours ago, and which should be about ready to finish was:
root@foo# dd if=/dev/hda of=/mnt/sda2/laptopdisk.dd.img

where hda is the internal laptop hard disk with the hosed windows installation (which is not mounted), and sda2 is the ext2 partition of the USB hard drive (which is mounted).

lspci indicates a usb 2.0 controller on the laptop:
0000:00:0b.2 USB Controller: VIA TEchnolgies, Inc. USB 2.0 (rev 51)

Sending a "kill -USR1" signal to the dd process spits out some in-progress stats--the latest shows:
38371893248 bytes transferred in 48138.170446 seconds (797120 bytes/sec)

I'm not sure what other commands I can run to find out more about where the slow down is occurring, but I'm all ears! It's not clear to me whether hdparm is something that can help me look at this, and I'm not sure if there are any usb diagnostics i can run to look at the interface while the transfer is going on.

Thanks in advance for any insight or shared experience. I was hoping an image would take less than 14 hours. :-)

Best Regards,
T

First off, I would use partimage instead of dd to image the partitions:

http://www.partimage.org/

Second, knoppix always transfers at usb1.1 speeds; I've never been able to speed it up to usb2.
I use kanontix which is based on knoppix but functions at usb2 speeds by default. Partimage is on both knoppix and kanontix by the eay.

Well that sure explains it. Ugh USB 1.1 speeds are indeed painful. How did you discover this about Knoppix, or is it a well know thing I've missed?

What's the advantage of using partimage? I can see it'd be faster as it doesn't save free blocks, but can you mount the resulting image file like a disk as you can with dd images, documented here: http://talk.trekweb.com/~jasonb/arti...loopback.shtml

Thanks again for your reply--it solved the mystery.

Knoppix has USB 2.0. You will have to use one of the four usb modules (uhci, ohci, usb-uhci, and usb-ohci). You can try to load ehci-hcd after you have removed uhci, ohci, usb-uhci, or usb-ohci ussing the rmmod command. I get better results with uhci with VIA chipsets though VMware complains about that module. VMware saids it can only handle usb-uhci.

Thanks Electro,

I did discover another issue that might be the culprit here as well. Buried in the non-printed manual for this Maxtor One Touch 250Gb external usb 2.0 drive is a ditty that says that you won't get full write speed until this thing has been power cycled 10 times. Dunno what the heck that's all about, but having powered it up only 4 times at most when this was done, I think that might also be to blame.

I'll be able to test it a little later, I'm curious to see if it was Knoppix or my failure to RTFM on this goofy drive requirement.

I've powered my maxtor one touch much more than 10 times, have ehci loaded and knoppix still gives me usb1.1 speeds and knoppix is the only distro where I've had this problem. Go figure.

Re your questions about partimage, no, you can't browse a partimage archive. Partimage's advantages over dd are that it's faster because only data blocks are copied; it gives about 2 to 1 compression; and it has a nice interface.
If you need to browse the archive, you could probably just use tar with compression for your backups but that won't work on ntfs, i.e. you could create the ntfs tar archive but you can't restore anything from it since linux doesn't support writing to ntfs.

Try other live LINUX CD distributions or re-compile the kernel for Knoppix to include support for USB 2.0. I think Knoppix has a tutorial how to do that.

You can send an e-mail to partition image developers to add support for viewing files from the image.

I use kanontix and get usb2 speeds. It's a livecd based on knoppix and gives you a debian testing if you install it to your hard drive.