Re: cloning to multiple drives with the "dd" command.

[didier chavaroche]

> Message du 18/02/15 16:45
> De : "Pádraig Brady" <address@hidden>
> A : "didier chavaroche" <address@hidden>, address@hidden
> Copie à :
> Objet : Re: cloning to multiple drives with the "dd" command.
>
> On 18/02/15 14:02, didier chavaroche wrote:
> > Hello.
> >
> >
> >
> > For a project of mine I need to clone one source drive to 23 target drives.
> > For this I am using the "dd" command that I execute 23 times.
> >
> > But it doesn't work, then I noticed doing it on 12 targets at once work fine.
> >
> > So I decided to split my cloning process into cloning first 12 targetss then clone the remaining 11 targets after.
>
> The two statements above seems to conflict?

Executing the "dd" command 23 time leads to transfert rate too low to be acceptable and in some case the cloning process

stops like 10min after it began.

Executing the "dd" command 12 time leads to a transfert rate about 100MB/s which is good for my application.

 

This why I decided to split the cloning process into two phases. To keep that 100MB/s transfert rate.

It is definitely faster that having to execute it 23 time.

> > But it doesn't work either, I don't know nor understand why it doesn't work?
> > Or if you have a technique so I can make my 23 drives at once.
>
> What failure do you see?
> Separate processes reading a single file and writing to separate devices,
> while somewhat inefficient, should work. If not it suggests a system issue,
> rather than one with dd.

 

Technicaly I don't see any failure. It is just that my tranfert rate is around 100MB/s for the first half

then it slows down to around 30MB/s for the second half which gravely affect the productivity of my system.
If it comes from the system there should be some command that I could use to restore 100MB/s

on the second half of the cloning process like flushing some cache or buffer.

> You might also want to try something higher level like:
> https://wiki.gnome.org/Apps/MultiWriter
>

 

Tank you, I will investigate on that matter. I already saw it can go up to 32GB, I need to go up to 500GB

But i'll see it anyway.

> cheers,
> Pádraig
>

 

Regards
Didier