Hi, I have a problem getting the performance up when writing to an external harddisk, connected via usb 2.0.
It shows when doing: i) cp file_from_local_sata_hdd to_usb_hdd_formatted_with_ext3fs_or_reiserfs ii) tar -xf file_from_local_sata_hdd -C/directory_on_usb_hdd_formatted_with_ext3fs_or_reiserfs iii) dd if=file_from_local_sata_hdd of=to_usb_hdd_formatted_with_ext3fs_or_reiserfs iv) all other stuff that incorporates writing to the disk, like creating encfs-files on it or trying to setup an encrypted loop device with yast on it. It shows on both opensuse 10.1 and 10.2, on a dual core centrino notebook (lenovo x60s) as well as on a dual core pentium desktop. No patched or self-built kernel or -modules are installed, all is pretty and default exept that all the latest packages from guru and packman are installed via smart. Performance figures look like this: CASE 1, writing onto the local sata disk: > dd if=/dev/zero of=tmp.txt count=1000 1000+0 records in 1000+0 records out 512000 bytes (512 kB) copied, 0.012393 seconds, 41.3 MB/s > CASE 2, "default" writing to the usb hdd, one can replace dd with cp or tar at will, the figures stay the same: > dd if=/dev/zero of=/media/usbdisk/tmp/tmp.txt count=1000 1000+0 records in 1000+0 records out 512000 bytes (512 kB) copied, 3.26417 seconds, 157 kB/s > CASE 3, notice the increased bs: > dd if=/dev/zero of=/media/usbdisk/tmp/tmp.txt count=4 bs=128K 4+0 records in 4+0 records out 524288 bytes (524 kB) copied, 0.033982 seconds, 15.4 MB/s > CASE 3 is what i would be expecting and what also what I get when writing to a fat32-partition on the external usb hdd. This also implies IMHO that there is nothing wrong with my usb-setup as suggested in various other postings regarding usb-performance. Here is an output regarding the usb-modules: >lsmod | grep hci ehci_hcd 34696 0 uhci_hcd 26892 0 usbcore 115024 3 usbhid,ehci_hcd,uhci_hcd > As suggested in http://marc.abramowitz.info/archives/2007/02/17/getting-good-performance-out-of-usb-hard-drives-in-linux/ I also tried fiddling with the value of /sys/block/sdX/device/max_sectors but with no significant success... I have created the ext3 and reiser partitions on the usb hdd with the yast partitioner, basically leaving everything at default settings. Any hints on where else to look for the cause of this poor performance? My workaround right now is to "copy" with: tar -cf - file_from_local_sata_hdd | tar -xf - -b2000 -C/directory_on_usb_hdd_ext3fs_or_reiserfs I am using -b2000 hereby to be able to do larger blocksized writes. Regards, Franz.
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