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

[Atin Mukherjee]

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.
Is this acceptable? If I have a,b,c sub directories in the volume and if
I mount the same volume in /mnt then do you mean to say I won't be able
to access /mnt/a or /mnt/b and I can only access them using sub
directory mounts? Or you are talking about some specific case here?
> 
> 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.
> 
> 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
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