Tag Archives: NoSAN

Cost vs Reward for the Nutanix Controller VM (CVM)

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I hear a lot of FUD (Fear Uncertainty and Doubt) getting thrown around about the Nutanix Controller VM (CVM) being a resource (vCPU/vRAM) hog.

So I thought I would address this perceived issue.

For those of you who are car people, you will understand the benefits of a Supercharger increasing performance of an engine.

The supercharger does this by attaching a belt to a pulley connected to the motor which spins the supercharger to force more air into the combustion chambers. This allows more fuel to be added to the mix to produce higher horsepower from the same engine displacement (engine capacity, ie: 2.0 Litres)

What is downside of a Supercharger?

The supercharger belt connected to the pulley can require even hundreds of horsepower to simply drive the supercharger. As such, a 300HP engine may have to use half of its power to just drive the supercharger.

So for example, a 300HP engine less 60HP (25%) to drive the supercharger equates to only 240HP remaining. But, as a result of the supercharger forcing more air into the engine, the engine now produces an additional 200HP.

So the “cost” of running the supercharger is 60HP, but the overall benefit is 200HP, resulting in the engine now producing 440HP.

Let’s now relate this back to the Nutanix Controller VM (CVM).

The CVM provides the storage features,functionality,excellent scalability and performance for the Virtual Machines. For example, reducing the latency thanks to Data Locality keeping data local to the compute node running the VM for faster reads and writes.

The faster the reads and writes, the less time VMs spend in a “CPU wait” state waiting for I/Os to be acknowledged by the storage which means the CPUs are being more efficiently utilized. This is a small part of the value the Nutanix CVM provides.

In Summary, the CVM does use some compute resources from the host (which depend on the node type and performance required) but like a Supercharger to an engine, the Nutanix CVM delivers significantly higher value to the VMs than the resources it uses.

Related Articles:

1. Rule of Thumb: Sizing for Storage Performance in the new world.

2. Is VAAI beneficial with Virtual Storage Appliance (VSA) based solutions ?

3. PART 1 – Problems with RAID and Object Based Storage for data protection

Can I use my existing SAN/NAS storage with Nutanix?

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I question I get regularly is, “Can I use my existing SAN/NAS storage with Nutanix?”.

The short answer is, as always “It depends”.

  • iSCSI, NFS & SMB 3.0 can be presented to Nutanix nodes just like existing non Nutanix nodes.
  • FC based storage cannot be used as Nutanix does not support FC HBAs

The below diagram shows a Nutanix NX-3460 block w/ 4 nodes having both Nutanix Containers presented to the nodes as well as iSCSI LUNs , SMB 3.0 or NFS Mount points connected from the centralized SAN/NAS.

Note: SMB 3 is not supported for ESXi hosts & NFS is not supported for Hyper-V.

Nutanix w External iSCSi NFS SMB Storage

So what is the use cases for this style of deployment?

If you’re not ready to do an entire infrastructure refresh for whatever reason/s, you may wish to transition to Nutanix over time while maximizing ROI and lifespan of you’re existing storage.

Here is some examples of what I recommend customers do:

1. Migrate Business Critical Applications (BCAs) to Nutanix

There are many benefits of doing this including:

  • Improving resiliency / performance for vBCAs
  • Simplifying storage management for vBCAs
  • Freeing up capacity and reducing the workload on legacy SAN
  • Increasing ease of scalability for critical workloads
  • Use legacy SAN/NAS for high capacity low IOPS workloads which are better suited to centralized storage than vBCAs

Another great option is

2. Migrate Virtual Desktops (VDI) to Nutanix which shares similar benefits to migrating vBCAs including:

  • Separating non complimentary VDI workloads from Server & vBCAs as these workloads do not mix well in centralized storage deployments
  • Improving resiliency / performance for VDI
  • Simplifying storage management for VDI
  • Reducing the workload on legacy SAN/NAS which will give an effective increase in performance for workloads remaining on the SAN/NAS
  • Increasing linear scalability for VDI for if/when the environment scales
  • Use legacy SAN/NAS for high capacity low IOPS workloads which are better suited to centralized storage than VDI

The last example I wanted to point out is Management workloads.

1. Migrate Infrastructure Management workloads to Nutanix.

As has been recommended by many industry experts, separating Management VMs from customer (e.g.: vCAC / vCloud tenants) or production server/desktop workloads (at both the Compute & Storage layers) can dramatically simplify the datacenter and help improve performance, resiliency & recoverability.

Again doing this provides similar benefits to the previous two examples.

  • Separating Management workloads from Server / vBCAs / VDI as these workloads should be separate from a security, resiliency, performance and recoverability perspectives.
  • Improving resiliency / performance for all workloads in the datacenter
  • Simplifying storage management for Management
  • Reducing the workload on legacy SAN/NAS which will give an effective increase in performance for workloads remaining on the SAN/SAN
  • Increasing scalability for if/when the management demands increase.
  • Maximizes the life span / performance of the legacy SAN/NAS

In summary, where it is not possible for budgetary reasons to migrate all workloads to Nutanix, migrating some workloads such as VDI, vBCA or Management to Nutanix will help alleviate the impact of scalability, performance and/or resiliency issues with your existing centralized SAN/NAS.

Nutanix also provides a solution which can start (very) small and continue to be scaled in a granular fashion over time until the SAN/NAS goes End of Life and/or when budget exists. At this time all workloads can then be migrated to Nutanix!

What does Exchange running in a VMDK on NFS datastore look like to the Guest OS?

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In response to the recent community post “Support for Exchange Databases running within VMDKs on NFS datastores” , the co-authors and I have received lots of feedback, of which the vast majority has been constructive and positive.

Of the feedback received which does not fall into the categories of constructive and positive, it appears to me as if this is as a result of the issue is not being properly understood for whatever reason/s.

So in an attempt to help clear up the issue, I will show exactly what the community post is talking about, with regards to running Exchange in a VMDK on an NFS datastore.

1. Exchange nor the Guest OS is not exposed in any way to the NFS protocol

Lets make this very clear, Windows or Exchange has NOTHING to do with NFS.

The configuration being proposed to be supported is as follows

1. A vSphere Virtual Machine with a Virtual SCSI Controller

In the below screen shot from my test lab, the highlighted SCSI Controller 0 is one of 4 virtual SCSI controllers assigned to this Virtual machine. While there are other types of virtual controllers which should also be supported, Paravirtual is in my opinion the most suitable for an application such as Exchange due to its high performance and low latency.

ExchangeVMSCSIController

2. A Virtual SCSI disk is presented to the vSphere Virtual Machine via a Virtual SCSI Controller

The below shows a Virtual disk (or VMDK) presented to the Virtual machine. This is a SCSI device (ie: Block Storage – which is what Exchange requires)

Note: The below shows the Virtual Disk as “Thin Provisioned” but this could also be “Thick Provisioned” although this has minimal to no performance benefit with modern storage solutions.

ExchangeVMVMDK

So now that we have covered what the underlying Virtual machine looks like, lets see what this presents to a Windows 2008 guest OS.

In Computer Management, under Device Manager we can see the expanded “Storage Controllers” section showing 4 “VMware PVSCSI Controllers”.

ExchangeVMPVSCSIController

Next, still In Computer Management, under Device Manager we can see the expanded “Disk Drives” section showing a number of “VMware Virtual disk SCSI Disk Devices” which each represent a VMDK.

 

 

ExchangeVMDeviceManager

 

 

 

 

Next we open “My Computer” to see how the VMDKs appear.

As you can see below, the VMDKs appear as normal drive letters to Windows.

ExchangeVMMyComputer

 

Lets dive down further, In “Server manager” we can see each of the VMDKs showing as an NTFS file system, again a Block storage device.

ExchangeVMDiskManager

Looking into one of the Drives, in this case, Drive F:\, we can see the Jetstress *.EDB file is sitting inside the NTFS file system which as shown in the “Properties” window is detected as a “Local disk”.

ExchangeVMFdriveProperties

So, we have a Virtual SCSI Controller, Virtual SCSI Disk, appearing to Windows as a local SCSI device formatted with NTFS.

So what’s the issue? Well as the community post explains, and this post shows, there isn’t one! This configuration should be supported!

The Guest OS and Exchange has access to block storage which meets all the requirements outlined my Microsoft, but for some reason, the fact the VMDK sits on a NFS datastore (shown below) people (including Microsoft it seems) mistakenly assume that Exchange is being serviced by NFS which it is NOT!

ExchangeVMDatastore

 

I hope this helps clear up what the community is asking for, and if anyone has any questions on the above please let me know and I will clarify.

Related Articles

1. “Support for Exchange Databases running within VMDKs on NFS datastores”

2. Microsoft Exchange Improvements Suggestions Forum – Exchange on NFS/SMB