[Linux-cluster] Clustered filesystem questions for shared storage on CentOS/vmWare/SAN

Digimer linux at alteeve.com
Fri Jan 13 20:44:28 UTC 2012

On 01/13/2012 03:30 PM, Wes Modes wrote:
> I have some general clustered filesystem questions for you.  I'm wading
> through the confusing and often contradictory web sources RE
> clustering.  I struggled through the initial setup of the GFS software,
> and am now working to create a shared GFS disk.  But all of this brings
> up some general questions:
> 1)  First several online sources have pointed me to the Microsoft
> Clustered Filesystem doc to set up my linux clustered FSs on vmWare. 
> Though it deals with MSCS, I can see that it has some applicability. 
> However, I have yet to find a step-by-step guide to linux clustered
> filesystems.  Is there a better suited document to guide me thorough the
> process of creating shared filesystems on CentOS/RHEL on vmWare across
> boxes? 
> 2)  Is it necessary to create a private network for access to the shared
> filesystem as the MSCS doc suggests?
> 3)  So far I've been looking at GFS because it is native to
> CentOS/RHEL.  Is there a better non-commercial/free choice?
> 4)  Is there a clustered filesystem method that supports vmWare HA? 
> This is important to us.
> 5)  Seems there at least three different methods to set up GFS (using
> parted, using lvmconf, and using iSCSI).  If I go with GFS, which method
> should I use?
> Clustering seems to have a steep learning curve, but I'm laboriously
> climbing the slope!  Thanks for your help.
> Wes Modes
> UCSC Library ITS
> Programmer/Analyst

Hi Wes,

  I can't speak to windows or VMWare as I have near-null experience with
both. So allow me to speak in general terms;

1. GFS2 is my preferred clustered file system, but it requires
distributed locking as provided by DLM, which is part of the Red Hat
Cluster Suite.

2. A private storage network is not required, but it is usually a good
idea simply because of how much traffic storage uses and how easy it is
to saturate a link and cause problems for other network stuff.

3. No. OCFS2 is the only other clustered file system I am aware of, and
it's under the control of Oracle. I shall say no more.

4. I'm not familiar with what requirements VMWare HA has. Can you
elaborate? In short though, all nodes take common storage and mount them
as local partitions/filesystems. Once done, your GFS2 partition is,
effectively, just another file system.

5. The storage layer and the file system should be independent of one
another. So long as the back-end storage presents said storage as raw
space to the nodes, GFS2 and the cluster shouldn't care. As for managing
that storage... That is effectively up to you. Personally, I like to use
clustered LVM on the raw storage, then create my GFS2 file system on an
LV. Of course, you can put the file system directly on the raw storage
and forego cLVM.

  I'm not sure how much this will help, given you want to use VMWare,
but I've got a tutorial that, among other steps, walks you through
setting up the base cluster , fencing (which is *required* for *any*
shared storage) and configuring and using the clustered LVM and GFS2 tools;


E-Mail:              digimer at alteeve.com
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