Re: dd too slow

From: Hactar (
Date: 12/20/03

Date: Sat, 20 Dec 2003 06:31:15 GMT

In article <>, Scott <root@localhost> wrote:
> I had to copy one HDD to another of same brand-size-model and it took more
> than 6 hours (I left it running) for 40GB UDMA 100 hard drives.
> I used these command options
> dd if=/dev/hda of=/dev/hdc bc=1M

It takes about an hour for two identical 120 GB drives (Hitachi
IC35L120AVV207-0), using the command

dd if=/dev/hda of=/dev/hdc bs={1,2,4,8,16}k

I'm trying to find the pattern that relates block size and total time. So
far it seems that doubling the block size reduces the total time by .5-1.5
minutes. Experiments continue...

> is this a normal speed for this size?

I'd say "no". Your drives are probably somewhat slower than mine (they're
smaller, after all), but 18 times slower is hard to believe.

> would hdparam do any good?

Check it out. Make sure DMA is on. Multi-sector transfers probably would
help too.

-eben    ebQenW1@EtaRmpTabYayU.rIr.OcoPm
          Q: What kind of modem did Jimi Hendrix use?
          A: A purple Hayes.