Drive Imaging with dd

[Lennart Sorensen]

On Thu, Aug 28, 2003 at 09:36:03AM -0400, Kareem Shehata wrote:
> Hey everyone,
> 
> I'm trying to image the XP partition on my laptop using Knoppix and an
> external 1394 drive.  I've gotten both drives up and running, and checked
> that both drives are running at full speed using hdparm:
> root at ttyp0[knoppix]# hdparm -t /dev/hda
> 
> /dev/hda:
>  Timing buffered disk reads:  64 MB in  3.19 seconds = 20.06 MB/sec
> root at ttyp0[knoppix]# hdparm -t /dev/sda
> 
> /dev/sda:
>  Timing buffered disk reads:  64 MB in  2.87 seconds = 22.30 MB/sec
> root at ttyp0[knoppix]# hdparm /dev/hda
> 
> /dev/hda:
>  multcount    = 16 (on)
>  I/O support  =  1 (32-bit)
>  unmaskirq    =  1 (on)
>  using_dma    =  1 (on)
>  keepsettings =  0 (off)
>  nowerr       =  0 (off)
>  readonly     =  0 (off)
>  readahead    =  8 (on)
>  geometry     = 4864/255/63, sectors = 78140160, start = 0
>  busstate     =  1 (on)
> 
> 
> When just dump the files directly from one drive to another, the
> performance is spot on:
> root at ttyp0[test]# dd if=/dev/hda1 of=shuttlepod.hda1
> 2260624+0 records in
> 2260624+0 records out
> 1157439488 bytes transferred in 64.225880 seconds (18021388 bytes/sec)
> 
> But the moment I stick gzip in the middle, is slows down by at least half:
> 
> root at ttyp0[test]# dd if=/dev/hda1 | gzip -1 > shuttlepod.hda1.gz
> 2563337+0 records in
> 2563336+0 records out
> 1312428032 bytes transferred in 203.288912 seconds (6455975 bytes/sec)
> 
> Any ideas on how to speed this up?  I've played with block size and
> compression levels, but I can't seem to do better than 10M/s.
> BTW: Anyone looking for motivation, my company is mainly a microsoft shop
> at the moment.  Ghost doesn't support 1394, and our laptops have USB1.1
> only.  Imaging used to be a pain (e.g. > 3 hours).  Not only would
> efficient imaging allow me to install linux on my laptop, it would prove a
> valuable tool.

Have you looked at top while running dd with gzip?  Might be CPU
limited.

Lennart Sorensen
--
The Toronto Linux Users Group.      Meetings: http://tlug.ss.org
TLUG requests: Linux topics, No HTML, wrap text below 80 columns
How to UNSUBSCRIBE: http://tlug.ss.org/subscribe.shtml