Ocfs2 users - Apr 2020 - mount existent ocfs2 volume in the local mode without the extra DLM, pacemaker/corosync layers

Hello Guys,

Usually, we create a ocfs2 cluster on the top DLM(pacemaker/corosync) with a
shared volume.
but the customers complained they could not mount existent ocfs2 volume in the
local mode without DLM/cluster envirnment in backup/restore scenario.
in this case, the customers want to mount this ocfs2 volume from one node
without cluster aware way, sometimes the customers have stoped(uninstalled) the
whole cluster before the backup/restore, they just want to access the data from
the ocfs2 volume.
Then, I'd like to add a mount option, e.g. "nocluster" (I feel
using "local" option is a little confused for the users, since we have
a local mount volume concept).
If the users use "nocluster" option to mount a ocfs2 volume, the whole
mount will not depend on the DLM/cluster related services. they
will mount the existent ocfs2 volume directly (like local mount) for avoiding
setup the cluster stacks.
The code change is small with my preliminary investigation, the main affected
places are mount.ocfs2/mounted.ocfs2 tools and mount process in the ocfs2 kernel
modules.

Any comments/suggestions? 


Thanks a lot
Gang

Hello Gang,

On 4/10/20 4:36 PM, Gang He wrote:
> Hello Guys,
> 
> Usually, we create a ocfs2 cluster on the top DLM(pacemaker/corosync) with
a shared volume.
> but the customers complained they could not mount existent ocfs2 volume in
the local mode without DLM/cluster envirnment in backup/restore scenario.
> in this case, the customers want to mount this ocfs2 volume from one node
without cluster aware way, sometimes the customers have stoped(uninstalled) the
whole cluster before the backup/restore, they just want to access the data from
the ocfs2 volume.
> Then, I'd like to add a mount option, e.g. "nocluster" (I
feel using "local" option is a little confused for the users, since we
have a local mount volume concept).
> If the users use "nocluster" option to mount a ocfs2 volume, the
whole mount will not depend on the DLM/cluster related services. they
> will mount the existent ocfs2 volume directly (like local mount) for
avoiding setup the cluster stacks.
> The code change is small with my preliminary investigation, the main
affected places are mount.ocfs2/mounted.ocfs2 tools and mount process in the
ocfs2 kernel modules.
Some quick questions:

1.Will the 'nocluster' ocfs2 volume be read-only?
2.How to achieve filesystem consistency if the whole cluster or some 
members of it crashed before this 'nocluster' mount.
3.Is there any mechanism guard protecting no other node do mount after 
this 'nocluster' mount.
4.Why do we have potential work for mounted.ocfs2?
5.I feel debugfs.ocfs2 can dump specified file or entire volume, is that 
satisfied for you?

Thanks,
Changwei

> 
> Any comments/suggestions?
> 
> 
> Thanks a lot
> Gang
> 
> _______________________________________________
> Ocfs2-devel mailing list
> Ocfs2-devel at oss.oracle.com
> https://oss.oracle.com/mailman/listinfo/ocfs2-devel
>

Just be curious about this user scenario.
What is "without DLM/cluster environment"?

Thanks,
Joseph

On 2020/4/10 16:36, Gang He wrote:
> Hello Guys,
> 
> Usually, we create a ocfs2 cluster on the top DLM(pacemaker/corosync) with
a shared volume.
> but the customers complained they could not mount existent ocfs2 volume in
the local mode without DLM/cluster envirnment in backup/restore scenario.
> in this case, the customers want to mount this ocfs2 volume from one node
without cluster aware way, sometimes the customers have stoped(uninstalled) the
whole cluster before the backup/restore, they just want to access the data from
the ocfs2 volume.
> Then, I'd like to add a mount option, e.g. "nocluster" (I
feel using "local" option is a little confused for the users, since we
have a local mount volume concept).
> If the users use "nocluster" option to mount a ocfs2 volume, the
whole mount will not depend on the DLM/cluster related services. they
> will mount the existent ocfs2 volume directly (like local mount) for
avoiding setup the cluster stacks.
> The code change is small with my preliminary investigation, the main
affected places are mount.ocfs2/mounted.ocfs2 tools and mount process in the
ocfs2 kernel modules.
> 
> Any comments/suggestions? 
> 
> 
> Thanks a lot
> Gang
> 
> _______________________________________________
> Ocfs2-devel mailing list
> Ocfs2-devel at oss.oracle.com
> https://oss.oracle.com/mailman/listinfo/ocfs2-devel
>

Hello Gang,

The option to mount without a clusterstack is: heartbeat=none

Give that a try and let us know if that doesn't work.

Thanks,
Herbert.

On 4/10/20 1:36 AM, Gang He wrote:
> Hello Guys,
>
> Usually, we create a ocfs2 cluster on the top DLM(pacemaker/corosync) with
a shared volume.
> but the customers complained they could not mount existent ocfs2 volume in
the local mode without DLM/cluster envirnment in backup/restore scenario.
> in this case, the customers want to mount this ocfs2 volume from one node
without cluster aware way, sometimes the customers have stoped(uninstalled) the
whole cluster before the backup/restore, they just want to access the data from
the ocfs2 volume.
> Then, I'd like to add a mount option, e.g. "nocluster" (I
feel using "local" option is a little confused for the users, since we
have a local mount volume concept).
> If the users use "nocluster" option to mount a ocfs2 volume, the
whole mount will not depend on the DLM/cluster related services. they
> will mount the existent ocfs2 volume directly (like local mount) for
avoiding setup the cluster stacks.
> The code change is small with my preliminary investigation, the main
affected places are mount.ocfs2/mounted.ocfs2 tools and mount process in the
ocfs2 kernel modules.
>
> Any comments/suggestions?
>
>
> Thanks a lot
> Gang
>
> _______________________________________________
> Ocfs2-devel mailing list
> Ocfs2-devel at oss.oracle.com
> https://oss.oracle.com/mailman/listinfo/ocfs2-devel