VMFS File Locking in VMware View 5.1 [WhitePaper]

VMware Technical Staff Jubish Jose has produced a detailed technical white paper that provides a thorough understanding of how VMFS File Locking mechanism impacts VMware View when used with View Composer to create Linked Clones.

It’s definitely an interesting reading, but as Duncan Epping points out “is that in vSphere 5.1 this “file sharing limit” has been increased from 8 to 32 for VMFS Datastores”. Cormac Hogan also wrote about this a while ago. VMware View does not yet support the new VMFS storage improvements that removes the 8 host limit for VMFS (only NFS).

However, the paper does provide some good insight on how VMFS locking and Linked Cloning work, and provide couple possible solutions.




In summary (if you cannot be bothered reading it), to allow vSphere Clusters with more than 8 hosts Administrators will need to place VMware View on NFS exports.




Another possible solution is to place only the Replica disk in a NFS export (This can be a dedicated replica datastore, or not). Be mindful when doing that because Linked Clones will use this Replica disk as source for reads, drastically increasing IO load and possible creating disk contention. Some storage arrays provide the flexibility to serve both Fiber Chanel or iSCSI and NFS from the same pool of disks.

If you want to better understand the IO behavior of Linked Clones I recommend reading my article entitled  The biggest Linked Clone “IO” Split Study.

The paper is available at http://www.vmware.com/files/pdf/techpaper/vmware-view-vmfs-file-locking.pdf


This article was first published by Andre Leibovici (@andreleibovici) at myvirtualcloud.net.

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