Nutanix Data Protection Capabilities

There is a lot of misinformation being spread in the HCI space about Nutanix data protection capabilities. One such example (below) was published recently on InfoStore.

Evaluating Data Protection for Hyperconverged Infrastructure

When I see articles like this, It really makes me wonder about the accuracy of content on these type of website as it seems articles are published without so much as a brief fact check from InfoStore.

None the less, I am writing this post to confirm what Data Protection Capabilities Nutanix provides.

  • Native In-Built Data protection

Prior to my joining Nutanix in mid-2013, Nutanix already provided a Hypervisor agnostic Integrated backup and disaster recovery solution with centralised consumer- grade management through our PRISM GUI which is HTML 5 based.

The built in capabilties are flexible and VM-centric policies to protect virtualized applications with different RPOs and RTOs with or without application consistency.

The solution also supports Local, remote, and cloud-based backups, and synchronous and asynchronous replication-based disaster recovery solutions.

Currently supported cloud targets include AWS and Azure as shown below.


The below video which shows in real time how to create Application consistent snapshots from the Nutanix PRISM GUI.

Nutanix can also perform One to One, One to Many and Many to One replication of application consistent snapshots to onsite or offsite Nutanix clusters as well as Cloud providers (AWS/Azure), ensuring choice and flexibility for customers.

Nutanix native data protection can also replicate between and recover VMs to clusters of different hypervisors.

  • CommVault Intellisnap Integration

Nutanix also provides integration with Commvault Intellisnap which allows existing Commvault customers to continue leveraging their investment in the market leading data protection product and to take advantage of other features where required.

The below shows how agentless backups of Virtual Machines is supported with Acropolis Hypervisor (AHV). Note: Commvault is also fully supported with Hyper-V and ESXi.

By Commvault directly calling the Nutanix Distributed Storage Fabric (NDSF) it ensures snapshots are taken quickly and efficiently without the dependancy on a hypervisor.

  • Hypervisor specific support such as VMware API Data Protection (VADP)

Nutanix also supports solutions which leverage VADP, allowing customers with existing investment in products such as Veeam & Netbackup to continue with their existing strategy until such time as they want to migrate to Nutanix native data protection or solutions such as Commvault.

  • In-Guest Agents

Nutanix supports the use of In-Guest agents which are typically very inefficient with centralised SAN/NAS storage but due to data locality and NDSF being a truly distributed platform, In-Guest Incremental forever backups perform extremely well on Nutanix as the traditional choke points such as Network, Storage Controllers & RAID packs have been eliminated.


As one size does not fit all in the world of I.T, Nutanix provides customers choice to meet a wide range of market segments and requirements with strong native data protection capabilities as well as 3rd party integration.

Integrity of I/O for VMs on NFS Datastores – Part 1 – Emulation of the SCSI Protocol

This is the first of a series of posts covering how the Integrity of I/O is ensured for Virtual Machines when writing to VMDK/s (Virtual SCSI Hard Drives) running on NFS datastores presented via VMware’s ESXi hypervisor as a “Datastore”.

Note: To be crystal clear, this post is not talking about presenting NFS direct to Windows or any other guest operating system.

This process is patented (US7865663) by VMware and its inventors and on the patent the process is called “SCSI Protocol Emulation”.

This series will first cover the topics in a vendor agnostic manner, meaning I am talking in general about VMware + any NFS storage on the VMware HCL with NFS support.

Following the vendor agnostic posts, I will follow with a series of posts focusing specifically on Nutanix, as the motivation for the series was to cover off this topic for existing or potential Nutanix customers, some of whom are less familiar with NFS and have asked for clarification, especially around virtualizing Business Critical Applications (vBCA) such as Microsoft SQL and Exchange.

The below diagram visualizes shows how storage can be presented to an ESXi host and what this series will focus on.

A VM accesses its .vmx and .vmdk file/s via a datastore the same way, regardless of the underlying storage protocol (DAS SCSI, iSCSI , NFS , FCP).


In the case of NFS datastores, SCSI protocol emulation is used to allow the Guest Operating System (OS) and application/s to read and write via SCSI even when the underlying storage (which is abstracted by the hypervisor) is served via NFS which does not natively support the same commands.

Image Source:

In the following section, and throughout this series, many images shown are from the patent (US7865663) and are the property of the patent owners, not the author of this article.

The areas which I will be focusing on are the ones where there has been the most concern in the industry, especially for business critical applications, such as Microsoft SQL and Microsoft Exchange, being how are the VM operating system and application/s (or data integrity) are impacted when issuing commands when the storage is abstracted by the hypervisor and served to via NFS which does not have equivalent I/O commands as SCSI.

Some examples areas of concern around the industry for VMs running on datastores backed by NFS are:

1. SCSI Aborts / Resets
2. Forced Unit Access (FUA) & Write Through
3. Write Ordering
4. Torn I/O (Writes + Reads)

In this first part, we will look at the SCSI Protocol Emulation process and discuss SCSI Aborts and Resets and how the SCSI protocol emulation process deals with these.

Below is a diagram showing the flow of an I/O request for a VM writing SCSI commands to a VMDK (formatted as NTFS) through the SCSI emulation process and through to the NFS storage.


The first few steps in my opinion are fairly self explanatory, where it gets interesting for me, and one of the points of contention among I.T professional (being SCSI aborts) is described in the box labelled “550“.

If the SCSI command is an abort (which has no equivalent in the NFS protocol), the SCSI emulation process removes the corresponding request from the virtual SCSI request list created in the previous step (box labelled “540“).

The same is true if the SCSI command is a reset (which also has no equivalent in the NFS protocol), the SCSI emulation process removes the corresponding request from the virtual SCSI request list. This process is shown below in the box labelled “560


Next lets look at what happens if the SCSI “abort” or “reset” command is issued after the SCSI emulation process has passed on the command to the storage and is now receiving a reply to a command which the Guest OS / Application has aborted?

Its quite simple, the SCSI emulation process receives a reply from the NFS server, looks up the corresponding tag in the Virtual SCSI request list, and because this corresponding tag does not exist, the emulator drops the reply therefore emulating a SCSI abort command.

The process is shown below from box labelled “710” to “720” and finishing at “730“.


In the patent, the above process is summed up nicely in the following paragraph.

Accordingly, a faithful emulation of SCSI aborts and resets, where the guest OS has total control over which commands are aborted and retried can be achieved by keeping a virtual SCSI request list of outstanding requests that have been sent to the NFS server. When the response to a request comes back, an attempt is made to find a matching request in the virtual SCSI request list. If successful, the matching request is removed from the list and the result of the response is returned to the virtual machine. If a matching request is not found in the virtual SCSI request list, the results are thrown away, dropped, ignored or the like.

So there we have it, that is how VMware’s patented SCSI Protocol emulation allows SCSI commands not supported natively by NFS to be honoured, therefore allowing applications dependant on Block based storage to be ran successfully within a VM where its VMDK is backed by NFS storage.

Let’s recap what we have learned so far.

1. The SCSI Commands, abort & reset have no equivalent in the NFS protocol.
2. The VMware SCSI Emulation process handles SCSI commands not supported natively by NFS thanks to the Virtual SCSI Request List.
3. Guest Operating Systems and Applications running in Virtual Machines on ESXi issue native SCSI commands to the NTFS volume, which is presented to the VM via a VMDK and housed on an NFS datastore.
4. The underlying NFS protocol is not exposed to the Guest OS, Application/s or Virtual Machine.
5. The SCSI Commands, abort & reset are emulated by the hyper visor through removing these requests from the Virtual SCSI emulation list.

In part two, I will discuss Forced Unit Access (FUA) & Write Through.

Integrity of Write I/O for VMs on NFS Datastores Series

Part 1 – Emulation of the SCSI Protocol
Part 2 – Forced Unit Access (FUA) & Write Through
Part 3 – Write Ordering
Part 4 – Torn Writes
Part 5 – Data Corruption

Nutanix Specific Articles

Part 6 – Emulation of the SCSI Protocol (Coming soon)
Part 7 – Forced Unit Access (FUA) & Write Through (Coming soon)
Part 8 – Write Ordering (Coming soon)
Part 9 – Torn I/O Protection (Coming soon)
Part 10 – Data Corruption (Coming soon)

Related Articles

1. What does Exchange running in a VMDK on NFS datastore look like to the Guest OS?
2. Support for Exchange Databases running within VMDKs on NFS datastores (TechNet)
3. Microsoft Exchange Improvements Suggestions Forum – Exchange on NFS/SMB
4. Virtualizing Exchange on vSphere with NFS backed storage?

Free Training – Virtualizing Business Critical Applications (vBCA)

Just found another great free self paced training course offered by VMware. This one is focused on one of my favourite topics, Virtualizing Business Critical Applications.

The course covers thing like what business critical applications can be virtualized efficiently as well as covering common customer objections, some of which are FUD or fiction.

In addition use cases, best practices and value propositions for virtualizing each business-critical application.

One important area the course covers (which can be hard to find reliable information on) is the licensing requirements for applications such as Oracle databases, SAP and the Microsoft Suite e.g.: SQL / Exchange / Sharepoint.

Kudo’s to VMware for releasing this training free of charge. The link to access the course is below.

Virtualizing Business-Critical Applications [V5.X] – Customer