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The Friday 2007-04-20 at 09:37 +0200, Franz Petri wrote:
> 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.
I would guess tar running slower in 'ii' above.
> 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
So the block size affects a lot. Curious!
My guess then would be that you perhaps are mounting "sync" mode, which is
very slow. Or the newer intermediate mode I forgot the name. You could
also benefit of mounting "noatime". Issue the command "mount" and see what
you have.
> I have created the ext3 and reiser partitions on the usb hdd with the
> yast partitioner, basically leaving everything at default settings.
There is a possibility I have not explored, and is having the journal in
the local filesystem instead, but I'm not sure how to accomplish that. I
think it would speed up things noticeably.
- --
Cheers,
Carlos E. R.
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