eNAS on VMAX3 and VAAI integration with NFS

Late last year in the second release of the HYPERMAX OS for VMAX3, EMC delivered new functionality for file-based storage called Embedded NAS or eNAS.  eNAS runs as a guestos (GOS) on the VMAX3 and therefore is fully integrated. What it does is enable virtual instances of VNX Software Data Movers and Control Stations to leverage a single platform creating a unified VMAX3 array, eliminating the need for the gateway product of the VMAX2 days.  In essence we have VNX technology in the VMAX3.  That brought me around to thinking about VMware in the VNX world and what features I might want to look at.  As I do a lot of work with VAAI I thought I’d start there.

Because eNAS is based on the VNX software, file systems configured on the VMAX3 can support VAAI. The feature in particular that NAS can take advantage of is NFS Clone Offload, though other features include extended stats, space reservations, and snap of a snap. In essence the NFS clone offload works much the same way as XCOPY as it offloads ESXi clone operations to the VNX Data Mover. The implementation of VAAI on VNX for NAS, however, is a manual process and is not enabled by default like block. It requires the installation of a plug-in on the ESXi host.

To install the plug-in, download the NAS plug-in from EMC support – EMCNasPlugin-2.0-4.zip. The plug-in is delivered as a VMware Installation Bundle (vib). The plug-in can be installed through VMware vCenter Update Manager or through the CLI – it will require a reboot.  Note that once installed VAAI is enabled for NFS and can only be disabled by uninstalling the plug-in.

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After reboot the vSphere Client will show that VAAI is supported on the NFS datastores.

eNAS_datastores_2Click to enlarge – use browser back button to return to post

You can also use the CLI to check support.

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Now that we have VAAI enabled, how can we tell if it is being used?  Well that’s a tricky one.  Unfortunately esxtop monitoring for VAAI does not include NFS, only block.  So other than perhaps seeing the host activity is less than usual, nothing here will help us.  Instead it is necessary to tail the vpxa.log file and search for “Vstorage” entries which will indicate that VAAI is being used.  The screenshot below is from a clone of a VM I ran on an NFS datastore.  You can see every 5 seconds the log is updated during the cloning process indicating the plug-in is being used until a completion message is issued.

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As I mentioned, one of the other VAAI integrations for NFS is extended stats. Using vmkfstools the user can display the disk utilization for virtual machine disks configured on NFS datastores.The extendedstat argument provides disk details for the virtual disks. The command reports, in bytes, virtual disk size, used space, and unshared space. This feature could be useful in scripting reports.

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Another VAAI capability on NFS is the ability to create a thin-clone virtual machine from an existing thin-clone virtual machine. This functionality is referred to as nested clones. The functionality uses the snapshot architecture to instantaneously create lightweight virtual machine clones. VMware products such as View Composer and vCloud Director use View Composer Array Integration (VCAI) to initiate virtual machine clones using the VNX Data Mover API for nested snapshots. The clone operations are off loaded to the VNX Data Mover. To take advantage of this feature, enable the nested clone support property when you create the file system as seen in this screenshot.  It cannot be changed after the file system is created.

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I’ll be including this detail in my latest update to the VAAI whitepaper for VMAX which I hope to have out by the end of March.  There’s some really good stuff for block VAAI and VMAX in the next release of vSphere so I need to wait for that to go GA before I can publish but you can be sure I’ll blog about it before I publish the paper…


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