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

Kaushal M kshlmster at gmail.com
Wed Mar 9 05:10:44 UTC 2016


On Tue, Mar 8, 2016 at 11:58 PM, Atin Mukherjee <amukherj at redhat.com> wrote:
>
>
> 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.

We use hardlinks to the `.glusterfs` directory on bricks. So wouldn't
having multiple filesystems inside a brick break the brick?

Also, I'd prefer if sub-directory mounts and sub-directory snapshots
remained separate, and not tied with each other. This mail gives the
feeling that they will be tied together.

>>
>> Pranith
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>> Gluster-devel at gluster.org
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