Gluster users - Jan 2013 - "Failed to perform brick order check,..."

Hi guys:

I have just installed gluster on a single instance, and the command:

gluster volume create gv0 replica 2 server.n1:/export/brick1
server.n1:/export/brick2

returns with:

"Failed to perform brick order check... do you want to continue ..?
y/N"?

What is the meaning of this error message, and why does brick order matter?

-- 
Jay Vyas
http://jayunit100.blogspot.com
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On 01/03/2013 12:51 PM, Jay Vyas wrote:
> Hi guys:
>
> I have just installed gluster on a single instance, and the command:
>
> gluster volume create gv0 replica 2 server.n1:/export/brick1 
> server.n1:/export/brick2
>
> returns with:
>
> "Failed to perform brick order check... do you want to continue ..?
y/N"?
>
> What is the meaning of this error message, and why does brick order 
> matter?
>
>
It's warning you that your replicated bricks will be on the same server, 
thus not providing hardware redundancy.

On 01/03/2013 12:51 PM, Jay Vyas wrote:
> Hi guys:
>
> I have just installed gluster on a single instance, and the command:
>
> gluster volume create gv0 replica 2 server.n1:/export/brick1 
> server.n1:/export/brick2
>
> returns with:
>
> "Failed to perform brick order check... do you want to continue ..?
y/N"?
>
> What is the meaning of this error message, and why does brick order 
> matter?
>
The second half of that question that I neglected to answer is that 
brick order matters due to establishing replica sets.

A replica set, "replica N" is each N bricks listed in order. So for
this
command:

    gluster volume create myvol1 replica 2 s1:/brick s2:/brick s3:/brick
    s4:/brick s5:/brick s6:/brick

There would be three replica sets, s1:/brick+s2:/brick, 
s3:/brick+s4:/brick, and s5:/brick+s6:/brick, that will be combined 
using distribute to create the volume myvol1.

If you wanted a little more redundancy, then:

    gluster volume create myvol2 replica 3 s1:/brick s2:/brick s3:/brick
    s4:/brick s5:/brick s6:/brick

Would create 2 replica sets, s1:/brick+s2:/brick+s3:/brick, and 
s4:/brick+s5:/brick+s6:/brick. Again they will be combined using 
distribute to create the volume myvol2.
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