Gluster users - Jul 2016 - gluster dispersed volume configuration

Hi everyone,

I am trying to configure a dispersed volume following this documentation 
page:

http://gluster.readthedocs.io/en/latest/Administrator%20Guide/Setting%20Up%20Volumes/#creating-dispersed-volumes

I have a set of 8 storage nodes, and I want the erasure coding settings 
to be (k=4)+(r=2). I understood that 6 bricks must be provided in order 
to create the volume. But my question is: is it possible to exploit the 
set of 8 servers given this coding configuration? My goal is the 
following: for each file, a set of 6 servers among the 8 is selected (in 
a round-robin way for example).

Regards,

Dimitri Pertin

Hi Dimitri,


On 06/07/16 18:13, Dimitri Pertin wrote:
> Hi everyone,
>
> I am trying to configure a dispersed volume following this documentation
> page:
>
>
http://gluster.readthedocs.io/en/latest/Administrator%20Guide/Setting%20Up%20Volumes/#creating-dispersed-volumes
>
>
> I have a set of 8 storage nodes, and I want the erasure coding settings
> to be (k=4)+(r=2). I understood that 6 bricks must be provided in order
> to create the volume. But my question is: is it possible to exploit the
> set of 8 servers given this coding configuration? My goal is the
> following: for each file, a set of 6 servers among the 8 is selected (in
> a round-robin way for example).
dispersed works with a fixed set of bricks, so you cannot directly do 
what you want only using disperse. However you can create a 
distributed-dispersed volume using 6 bricks in each storage node. This 
way you can create 8 disperse subvolumes, each of them using exactly 6 
bricks and fully using all 8 storage nodes.

In a "graphical" way:

Storage node:      1 2 3 4 5 6 7 8
Disperse subvol 1: x x x x x x
Disperse subvol 2:   x x x x x x
Disperse subvol 3:     x x x x x x
Disperse subvol 4: x     x x x x x
Disperse subvol 5: x x     x x x x
Disperse subvol 6: x x x     x x x
Disperse subvol 7: x x x x     x x
Disperse subvol 8: x x x x x     x

The command line would be something like this:

gluster volume create test disperse 6 redundancy 2 \
     S1:/B1 S2:/B1 S3:/B1 S4:/B1 S5:/B1 S6:/B1 \
     S2:/B2 S3:/B2 S4:/B2 S5:/B2 S6:/B2 S7:/B1 \
     S3:/B3 S4:/B3 S5:/B3 S6:/B3 S7:/B2 S8:/B1 \
     S4:/B4 S5:/B4 S6:/B4 S7:/B3 S8:/B2 S1:/B2 \
     S5:/B5 S6:/B5 S7:/B4 S8:/B3 S1:/B3 S2:/B3 \
     S6:/B6 S7:/B5 S8:/B4 S1:/B4 S2:/B4 S3:/B4 \
     S7:/B6 S8:/B5 S1:/B5 S2:/B5 S3:/B5 S4:/B5 \
     S8:/B6 S1:/B6 S2:/B6 S3:/B6 S4:/B6 S5:/B6

Where Sx are the storage servers and Bx are the bricks in each server.

Xavi
>
> Regards,
>
> Dimitri Pertin
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