GFS without fencing

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Dear All,

I want to setup shared file systems between 4 RHEL Boxs. After researching GFS and OCFS2, it seems to me that GFS is more complicated to setup than OCFS2, especially fencing methods. Could you help me know is there any way to setup GFS without using any fencing mothods?

Thanks in advance.

PS: Sorry if my English is poor.

Responses

Dear Peter,

"Setup shared file systems between 4 RHEL Boxs" --> you want setup file server cluster with RHCS?

GFS2 is not complecated compare to OCFS2. However you have OCFS for RHEL5 not for 6, as I know. However you can install GFS from repo. In case of OCFS you will have download and install packages manually.

Fencing is a issue about fencing fult nodes when nodes are trying to rejoing in cluster to reduce split brain issue. According to your query, I think GFS has nothing to do with fencing.

Please suggest if I am wrong.

 

rgds,

Shyfur

Hi,

When no fence device is configured for a node or the configured fence method is unsuccessful, and that node must be removed from the cluster, the cluster will repeatedly attempt to fence that node until it is successful or until it rejoins after a complete restart (ie reboot). This will cause cluster services such as clvmd, rgmanager, cmirror, and GFS/GFS2 file systems to become inoperable, and may manifest itself as commands that rely on the cluster infrastructure hanging.

Please see

https://access.redhat.com/knowledge/solutions/160563  Why do lvm commands hang, GFS/GFS2 file systems become unresponsive, and cluster operations hang when fencing is failing in a cluster?

https://access.redhat.com/knowledge/solutions/15575 What is fencing and why is it important?

 

Thank you

Nitin Yewale

Thanks Mr.Shyfur and Mr. Mitin,

Do you means that if I setup GFS/GFS2 only for sharing files between servers without cluster services such as clvmd, rgmanager, cmirror..., fencing is not required but if I use it with cluster services , fencing is necessary?

Thank you and best Regards.

Hello Peter,

When the gfs2 fs is shared between servers, cluster of the nodes sharing the FS is *must*. For details on configuring the same, please see  

https://access.redhat.com/knowledge/solutions/16664 What is the recommended LVM configuration when multiple Red Hat Enterprise Linux cluster nodes are accessing the same shared storage?

(I believe this is not the setup of NFS server and 4 clients sharing the FS. )

 

Regards,

Nitin Yewale

Hello peter,

If you are thinking about cluster, Fencing is necessary. As I said, to avoid split brain scenario. Please follow this below link. May be these links will guid you.

 

https://access.redhat.com/knowledge/solutions/54453

https://access.redhat.com/knowledge/node/28603

Thanks,

Shyfur

Hello Mr.Shyfur and Mr. Mitin,

Thanks for your suggestions.

One of my fears is that fencing may be complicated to configure and I don't want my server is force to be off by fencing when it can not communicate with other servers. Because there are some services that do not stop properly.

Regards.

Hello Peter,

>>

I don't want my server is force to be off by fencing when it can not communicate with other servers.

>>

What server are you planning to use ? OR what is the fence device you are planning to use ? The default action of fencing is to reboot the server. When the nodes are not able to communicate with each other, they will try to fence each other assuming the other one is not available also knows as " split brain " or fence race. In order that one node remains up and continue running service, we can use "delay" option of fencing. For details, please see

https://access.redhat.com/knowledge/solutions/54829 Delaying Fencing in a Two Node Cluster to Prevent Fence Races or "Fence Death" Scenarios

 

Best Regards,

Nitin Yewale

Hi Mr. Nitin,

I'm using it for some java applications that process important data. In future, I have been planning to run Core Banking on RHEL servers, but sharing FS between them make me worried when I need to share data effectively between nodes. I am researching more about this to find best solution. GFS/GFS2 may be very good but fencing is my worry.

Regards,

Hello Peter,

Glad to know you will be using RHEL. Please let us know how we could help you futher on this. Please note fencing is *must* in RHEL clusters.

 

Best Regards,

Nitin Yewale