[Linux-cluster] Data Loss / Files and Folders "2-Node_GFS-Cluster"

[Wendy Cheng]

Doug Tucker wrote:
>   
>> I don't (or "didn't") have adequate involvements with RHEL5 GFS. I may 
>> not know enough to response. However, users should be aware of ...
>>
>> Before RHEL 5.1 and community version 2.6.22 kernels, NFS locks (i.e. 
>> flock, posix lock, etc) is not populated into filesystem layer. It only 
>> reaches Linux VFS layer (local to one particular server). If your file 
>> access needs to get synchronized via either flock or posix locks 
>> *between multiple hosts (i.e. NFS servers)*,  data loss could occur. 
>> Newer versions of RHEL and 2.6.22-and-above kernels should have the code 
>> to support this new feature.
>>
>> There was an old write-up in section 4.1 of 
>> "http://people.redhat.com/wcheng/Project/nfs.htm" about this issue.
>>
>> -- Wendy
>>
>> --
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>> Linux-cluster at redhat.com
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>>     
>
> Wendy,
>
> To be clear, does this include RHEL 4.7, or is it specific to 5.x?
>   

The changes were made on 2.6.22 kernel. I would think RHEL 4.7 has the 
same issue - but I'm not sure as I left Red Hat before 4.7 was released. 
Better to open a service ticket to Red Hat if you need the fix.

If applications are directly run on GFS nodes, instead of going thru NFS 
servers, posix locks and flocks should work *fine* across different 
nodes. The problem had existed in Linux NFS servers for years - no one 
seemed to complain about it until clusters started to get deployed more 
commonly.

-- Wendy