[Gluster-devel] Simplify creation and set-up of meta-volume (shared storage)

[Avra Sengupta]

Hi,

A shared storage meta-volume is currently being used by 
snapshot-scheduler, geo-replication, and nfs-ganesha. In order to 
simplify the creation and set-up of the same, we are introducing a 
global volume set option(cluster.enable-shared-storage).

On enabling this option, the system analyzes the number of peers in the 
cluster, which are currently connected, and chooses three such 
peers(including the node the command is issued from). From these peers a 
volume(gluster_shared_storage) is created. Depending on the number of 
peers available the volume is either a replica 3 volume(if there are 3 
connected peers), a replica 2 volume(if there are 2 connected peers), or 
a single brick volume(if there is only one node in the cluster). 
"/var/run/gluster/ss_brick" serves as the brick path on each node for 
the shared storage volume. We also mount the shared storage at 
"/var/run/gluster/shared_storage" on all the nodes in the cluster as 
part of enabling this option.

Once the volume is created, and mounted the maintainance of the volume 
like adding-bricks, removing bricks etc., is expected to be the onus of 
the user.

On disabling the option, we provide the user a warning, and on 
affirmation from the user we stop the shared storage volume, and unmount 
it from all the nodes in the cluster.

These are achieved with hook-scripts as part of the volume set option. 
If anyone is interested in having a look at the patch, it's available 
for review at http://review.gluster.org/#/c/10793/ . If there is any 
feedback and suggestion regarding the same, please feel free to share it.

Regards,
Avra