Re: How long does DD take? 180GB?
From: Paul Lutus (nospam_at_nosite.zzz)
Date: 10/06/03
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Date: Mon, 06 Oct 2003 09:43:35 -0700
Frank Burns wrote:
> I had a 360GB RAID (2 X WD 1800JB) and one of the harddrives started
> acting funny, and thus my RAID went offline. So I got 2 replacement
> drives, and I am in the process of using DD to copy the entire
> harddrive to the replacement harddive, (X 2) and hopefully, I will
> just put the 2 replacement harddrives back into my computer, and it
> will work (cross fingers, ~330GB of data is not fun to loose) Both
> harddrives check out fine in WD's driver utilities. For now, which is
> good. Anyways, so I am using DD to copy the entire partition. I
> booted to linux from CDRom, and use the DD command to copy one
> harddrive to the other. Here I am sitting, it's 16 hours + into the
> operation, and it's not done.
Did you run this on both drives:
# hdparm -Tt /dev/hd(a-d) (tests drive r/w speeds)
> I have the source HDD on secondard
> slave, and the destination HDD on primary secondary. 180GB / 16 hours
> it about 3 megs/second, minimum. It's still not done. Is this
> normal?
Do the math. 3 megabytes per second, 360 GB total, assuming the drive is
full or you are copying an image (you are, since you are using dd). That
is:
360e9/3e6 = 120,000 seconds = 33 1/3 hours. This doesn't take read time into
account, it could be double this value.
> If I would have installed Linux on a HDD would this go
> faster?
If you had only copied the files, not the disk image, it would be faster
unless the drive is completely full.
> Is DMA not installed?
Why are you asking us? Run this on the HDD:
$ hdparm /dev/hd(a-d) (lists setup parameters)
And a HDD without DMA enabled can easily be reduced to 3 MB/s.
-- Paul Lutus http://www.arachnoid.com
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