I'm configuring a 4 node Oracle VM environment. One management server, two vm servers and a storage server with direct attached storage.

The storage server is running Linux and I thus have the option of providing the shared storage for the VM servers on iSCSI (with OCFS2) or NFS.

Is it likely that one would perform better or more reliably than the other? Any other things one should take into consideration when deciding between the two?

Note that Oracle VM is the Xen based virtualization product from Oracle, not a generic term for virtualized Oracle databases.

  • Why do you have two DB servers but a single point of failure with the way you're doing storage? – Chopper3 Nov 10 '09 at 19:19
  • It's for staging. Production have better budgets :) – Roy Nov 10 '09 at 19:32

All other things being equal, I would expect a block-level protocol (iSCSI) to beat out a file-level protocol (NFS) performance-wise.

An NFS storage area (file system) can be shared simultaneously by more than one host, the storage server's OS would be responsible for arbitrating access to files. You could more easily share a pool of storage for both servers this way. For hosting Oracle VM data, this may be a fairly unimpressive benefit.

iSCSI has the advantage of making the storage available as a block device. This is likely to be more similar to your production environment. The drawback is that only one host can attach to each iSCSI target at a time.

I do not know that one would be significantly more reliable than another, but I have a preference for iSCSI.

Your backup strategy may vary somewhat depending on which solution you go with.

  • More than one host can attach at the same time - VMFS, part of VMware, will arbitrate access between hosts. – Jim Zajkowski Nov 10 '09 at 22:36
  • True! I have not had the privilege of trying out VMFS before. – Jeremy Nov 10 '09 at 23:15
  • +1 for backup strategy considerations – Roy Nov 11 '09 at 14:26
  • 1
    Since we're talking the Xen based Oracle VM (and not VMware) I don't think VMFS is viable. However, this is shared storage and Oracle VM uses OCFS2 for this. Both iSCSI and multipath devices are supported. Jim's point is still valid, though. Multiple hosts can (and have to) be attached to the same iSCSI target at the same time for the Live Migration and HA functionality to be available. – Roy Nov 11 '09 at 14:27

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