Is this a DD bug?

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Is this a DD bug?

by daniel_nysveen :: Rate this Message:

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Hi,

I have a strange dd problem when running the dd command on brand new hard drives. I am often creating clones of hard drives and I have come across something I don't understand. If I DD to a hard drive that has been previously used, the DD takes about 35 minutes. If I clone to a completely brand new drive, the DD takes over 100 minutes. If I immediately run the DD command again, on the same set of drives, the DD now only takes 35 minutes. Do you have any ideas on what is going on?

Thank you,

Daniel Nysveen

Re: Is this a DD bug?

by Pádraig Brady :: Rate this Message:

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daniel_nysveen@... wrote:
>
> I have a strange dd problem when running the dd command on brand new hard drives.
> If I DD to a hard drive that has been previously used, the DD takes about 35 minutes.
> If I clone to a completely brand new drive, the DD takes over 100 minutes.
> If I immediately run the DD command again, on the same set of drives, the DD now only takes 35 minutes.

Very unlikely to be anything to do with dd.
Are these SSDs ? What block size are you using?
What size are the disks. What kernel version are you using.
Maybe `strace -e write -T dd ...` might point to something.

cheers,
Pádraig.