[Gluster-devel] sub-directory geo-replication, snapshot features

[Aravinda]

regards
Aravinda

On 03/08/2016 07:32 PM, Pranith Kumar Karampuri wrote:
> hi,
>          Late last week I sent a solution for how to achieve 
> subdirectory-mount support with access-controls 
> (http://www.gluster.org/pipermail/gluster-devel/2016-March/048537.html). 
> What follows here is a short description of how other features of 
> gluster volumes are implemented for sub-directories.
>
> Please note that the sub-directories are not allowed to be accessed by 
> normal mounts i.e. top-level volume mounts. All access to the 
> sub-directories goes only through sub-directory mounts.
>
> 1) Geo-replication:
> The direction in which we are going is to allow geo-replicating just 
> some sub-directories and not all of the volume based on options. When 
> these options are set, server xlators populate extra information in 
> the frames/xdata to write changelog for the fops coming from their 
> sub-directory mounts. changelog xlator on seeing this will only 
> geo-replicate the files/directories that are in the changelog. Thus 
> only the sub-directories are geo-replicated. There is also a 
> suggestion from Vijay and Aravinda to have separate domains for 
> operations inside sub-directories for changelogs.
We can additionally record subdir/client info in Changelog to 
differentiate I/O belonging to each subdirs instead of having separate 
domains for changelogs.

Just a note, Geo-replication expects target to be Gluster Volume and not 
any directory. If subdir 1 to be replicated to remote site A and subdir2 
to be replicated to remote site B, then we should have two Geo-rep 
session from Master to two remote volumes in remote site A and site B 
respectively.(with subdir filter accordingly)
>
> 2) Sub-directory snapshots using lvm
> Every time a sub-directory needs to be created, Our idea is that the 
> admin needs to execute subvolume creation command which creates a 
> mount to an empty snapshot at the given sub-directory name. All these 
> directories can be modified in parallel and we can take individual 
> snapshots of each of the directories. We will be providing a detailed 
> list commands to do the same once they are fleshed out. At the moment 
> these are the directions we are going to increase granularity from 
> volume to subdirectory for the main features.
>
> Pranith