[Ocfs2-devel] mount existent ocfs2 volume in the local mode without the extra DLM, pacemaker/corosync layers

[Gang He]

Hi Joseph,

________________________________________
From: Joseph Qi <joseph.qi at linux.alibaba.com>
Sent: Friday, April 10, 2020 8:49 PM
To: Gang He; Joseph Qi; ocfs2-devel at oss.oracle.com; ocfs2-users at oss.oracle.com
Subject: Re: [Ocfs2-devel] mount existent ocfs2 volume in the local mode without the extra DLM, pacemaker/corosync layers



On 2020/4/10 18:16, Gang He wrote:
> Hello Jeseph,
>
> ________________________________________
> From: Joseph Qi <jiangqi903 at gmail.com>
> Sent: Friday, April 10, 2020 6:00 PM
> To: Gang He; ocfs2-devel at oss.oracle.com; ocfs2-users at oss.oracle.com
> Subject: Re: [Ocfs2-devel] mount existent ocfs2 volume in the local mode without the extra DLM, pacemaker/corosync layers
>
> Just be curious about this user scenario.
> What is "without DLM/cluster environment"?
>
> The user can mount the existent ocfs2 cluster volume directly, does not depend on if DLM/cluster services are available.
> When this option is added, the mount process  will not do dlm related things, like local mount.
> This way will help the user access the files in the volume quickly for avoiding setup/online the cluster environment.
>
But it is cheap to online cluster, even there is only one node, right?

You know, ocfs2 uses two cluster stack (o2cb and pcmk).
If the user select pcmk stack to setup a ocfs2 cluster file system, 
they need to setup a pacemaker cluster according to the guide,
then they need to add some configurations(e.g. stonith/dlm resource) via pacemaker shell interface.
the whole setup process is a little heavy for the user. 

Thanks
Gang
 



>
> 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
>>
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>>
>
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