increasing dd disk to disk transfer rate

[Eric Anderson]

Christoph Kukulies wrote:

>My notebooks' hard disk, a Hitachi Travelstar 80 GB starts to develop read
>errors. I have FreeBSD and Win XP on that disk. Although FreeBSD ist still
>working , the errors in the Windows partition are causing Windows do ask for a 
>filesystem check nearly everytime I reboot the computer. One time the
>error was in the hibernate.sys file, which impedes powering up quickly after
>a hibernate.
>
>Anyway, I decided to buy a second identical hard disk and tried to
>block by block copy the old disk to the new one using
>
>dd if=/dev/ad2 of=/dev/ad3 conv=noerror
>  
>

Specify a larger block size - the default is 512bytes, which is not 
efficient for what you are doing.  Maybe 1mb would be the right number.

>The process is running now since yesterday evening and it is at 53 MB
>at a transfer rate of about 1.1 MB/s.
>
>In case the the result being unusable I would like to find a way to make this
>copying faster.
>
>Any disk expert here? My motherboard is an ASUS P4S8X with an on board
>promise controller (currently not in use). System disk is
>on IDE1 and the two 80GB disks are master/slave on IDE2 bus.
>  
>

Also, put the disks on separate IDE busses - one disk on ide1, the other 
on ide2.  This will help a lot..

>I wonder wether I could get better results (transfer rate) when attaching the
>disks to copy to the promise IDE bus.
>
>And another question:
>
>Is there a way to tweak the driver (be it the FreeBSD promise driver
>or the normal ata driver) to use more retries on errors so that I
>have the chance to copy everything or nearly everything of the already
>degrading hard disk?
>


Not sure about that..

Eric


-- 
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Eric Anderson        Sr. Systems Administrator        Centaur Technology
Anything that works is better than anything that doesn't.
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