[Gluster-devel] Read-only option for a replicated (replication for fail-over) Gluster volume

[Samikshan Bairagya]

On 03/21/2017 12:38 AM, Mackay, Michael wrote:
> Gluster folks:
>
> Our group has a need for a distributed filesystem, like Gluster, that can be mounted by clients as read-only.  We wish to have the ability to seamless switch over to an alternate source of this read-only data if the default source fails.
> The reason for this ROFS is so that every client can get access to applications and data that we want to ensure stays the same (unmodifiable) for an entire system delivery life cycle. To date we've used read-only NFS mounts reasonably well, but its failover performance is not at all great.
>
> We also don't want a "WORM" sort of arrangement - we want to prevent any and all writes to the volume once it's up and shared.
>
> So, under the "how hard could it be" mantra, we took version 3.7.15 and poked around a bit until we got it to do just what we want.  It was a minor mod to 'xlators/features/index/src/index.c' and 'xlators/storage/posix/src/posix-helpers.c', along with a "force" option when doing the volume start command.
>
> We would happily share the specific changes, and they seem to fit in the 3.10.0 code base too; the question for the group is, would such a capability be of interest to the Gluster baseline?  Possibly a precursor question (since I don't have much experience in gluster-devel at all, so please forgive my approach if it's wrong) is, to whom should I pose this question, if it's not to this group?
>
> Thanks for your time and I'd be happy to provide any further information.
>

Hi Mike,

Have you checked the 'features.read-only' volume option. Apparently you 
can set it to on/off depending on whether you want your volume to be 
read-only or not. By default it is set to 'off'. The following would 
make your volume read-only for all clients accessing it:

# gluster volume set <VOLNAME> features.read-only on

Hope that helped.

~ Samikshan