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I'm in the process of migrating our cluster to new hardware. We use bare metal servers, no virtualization.

Currently, we have around 30 "application" servers. When we make an update, we push the changes to one machine, then use lsync (a branch of rsync) to push the new files to all of the machines in the cluster.

My new idea was to use a SAN along with iscsi to simply "share" the app across all servers from one location. Little did I know that you can't really do that out of the box. Each machine slices out its own piece of the SAN, but the machines can't see each others files.

What is the best way around this? We're running Centos 6.4 on all of the machines. I stumbled across this, but have heard mixed things about running a clustered filesystem http://ricardobaylon.wordpress.com/2013/11/11/centos-6-4-cluster-gfs-iscsi/

Brian Lovett
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Get a NAS instead of a SAN and export the file system via NFS.

As you've discovered SANs share block storage via networking protocols like iSCSI, ATAoE, or FibreChannel. NAS devices share file systems over protocols such as NFS, CIFS/SMB, WebDAV, and possibly others.

See also: What is the difference between SAN, NAS and DAS?

Community
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Chris S
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    One still can use iSCSI lun shared if used with cluster aware FS like ocfs, but i agree on using NFS, some SANS give you NFS option now. – Danila Ladner Jan 30 '14 at 21:42
  • Deep down I knew this was the answer already.... – Brian Lovett Jan 30 '14 at 21:45
  • just connect via linux iscsi initiator from every server and mount, use ocfs2. Worked for me. You could allocate the heartbeat device on a separate LUN, it is more robust this way. – Danila Ladner Jan 30 '14 at 21:47
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    Shared Storage file systems certainly would work, but add an extra layer of complexity with no obvious benefit to this situation. – Chris S Jan 30 '14 at 22:47
  • THe more I dug into it, the more complexity it seemed to add for no real reason. I initially thought about running ocfs or gfs, but maintaining the config on each machine, especially when we add new machines regularly... It gets to be needless complexity. – Brian Lovett Jan 31 '14 at 16:56
  • Thumbs up for the NAS suggestion. SAN has its place but it is overused and much more of a management headache compared to NFS or even Samba. – Mark May 22 '14 at 14:24