Tag Archives: best practice

SQL & Exchange performance in a Virtual Machine

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The below is something I see far to often: An SQL or Exchange virtual machine using a single LSI Logic SAS virtual SCSI controller.

LSIlogic

What is even worse is a virtual machine using a single LSI controller and a single virtual disk for one or more databases and logs (as shown above).

Why is this so common?

Probably because the LSI Logic SAS controller is the default for Windows 2008/2012 virtual machines and additional SCSI controllers are not automatically added until you have more than 16 virtual disks for a single VM.

Why is this a problem?

The LSI controller has a queue depth limit of 128, compared to the default limit for PVSCSI which is 256, however it can be tuned to 1024 for higher performance requirements.

As a result, the a configuration with a single LSI controller and/or a limited number of virtual disks can artificially significantly constrain the underlying storage from delivering the performance it is capable of.

Another problem with the LSI controller is the amount of CPU it uses is higher than the PVSCSI controller for the same IO levels. This means you’re wasting virtual machine (and the underlying hosts) CPU resources unnecessarily.

Using more CPU could lead to other problems such as CPU Ready which can also lead to reduced performance.

A colleague and friend of mine, Michael Webster wrote a great post titled: Performance Issues Due To Virtual SCSI Device Queue Depths where he shows the performance difference between SATA, LSI and PVSCSI controllers. I highly recommend having a read of this post.

What is the solution?

Using multiple Paravirtual (PVSCSI) adapters with virtual disks evenly spread over the four controllers for Windows virtual machines is a no brainer!

This results in:

  1. Higher default queue depth
  2. Lower CPU overheads
  3. Higher potential performance

How do I configure this?

It’s fairly straight forward, but don’t just change the LSI Controller too PVSCSI as the Guest OS may not have the driver installed which will result in the VM failing to boot.

Too avoid this, simply edit the virtual machine and add a new Virtual Disk of any size and for the virtual device node, select SCSI (1:0) and follow the prompts.

VirtualDiskSCSI10

Once the new virtual disk is added you should see a new LSI Logic SAS SCSI controller is added as shown below.

NewLSIController

Next highlight the adapter and select “Change Type” in the top right hand corner of the window and select Paravirtual. Once this is complete you should see similar to the below:

AddPVSCSIController

Next hit “Ok” and the new Controller and virtual disk will be added to the VM.

Now we open the console of the VM and open Compute Management and goto Device Manager. Under Storage Controllers you should now see VMware PVSCSI Controller as shown below.

DeviceManagerPVSCSI

Now we are safe to Shutdown the VM.

Once the VM is shutdown, Edit the VM setting and highlight the SCSI Controller 0 and select Change Type as we did earlier and select Paravirtual. Once this is done you will see the original controller is replaced with a new controller.

ChangeLSItoPVSCSI

Now that we have the boot drive change to PVSCSI, we can now balance the data drives across up to four PVSCSI controllers for maximum performance.

To do this, simply highlight a Virtual Disk and drop down the Virtual Device Node and select SCSI (1:0) or any other available slot on the SCSI (1:x) controller.

ChangeControllerID

After doing this you will see new SCSI controllers appear and you need to change these to Paravirtual as we have done to the first controller.

ChangeControllerIDMultipleVdisks

For each of the virtual disks, ensure they are placed evenly across the PVSCSI controllers. For example, if you have a VM with eight virtual disks plus the OS disk, it should look like this:

Virtual Disk 1 (OS) : SCSI (0:0)
Virtual Disk 2 (OS) : SCSI (0:1)
Virtual Disk 3 (OS) : SCSI (1:0)
Virtual Disk 4 (OS) : SCSI (1:1)
Virtual Disk 5 (OS) : SCSI (2:0)
Virtual Disk 6 (OS) : SCSI (2:1)
Virtual Disk 7 (OS) : SCSI (3:0)
Virtual Disk 8 (OS) : SCSI (3:1)
Virtual Disk 9 (OS) : SCSI (0:2)

This results in two data virtual disks per PVSCSI controller which evenly distributes IO across all controllers with the exception being first controller (SCSI 0) also hosting the OS drive.

What if I have problems?

On occasions I have seen problems with this process which has resulted in VMs not booting, however these issues are easy to fix.

If your VM fails to boot with a message like “Operating System not found”, I suggest you panic! Just kidding, this is typically just the boot order of the Virtual machine has been screwed up. Just go into the bios and check the boot order has the PVSCSI controller showing and the correct virtual disk in first priority.

If the VM boots and BSOD or crashes and goes into a continuous reboot loop then power off the VM and set the first SCSI controller where the boot disk is running back to LSI. Then reboot the VM and make sure the PVSCSI driver is showing up (if its not you didn’t follow the above instructions) so go back and follow them so the PVSCSI driver is loaded and working, then shutdown and change the SCSI controller back to PVSCSI and you should be fine.

If the VM boots and one or more drives do not show up in my computer, go into Disk Manager and you may see the drives are marked as offline. Simply right click the drive and mark it as online and reboot and you’re good to go.

Summary:

If you have made the intelligent move to virtualize your business critical applications, firstly congratulations! However as with physical hardware, Virtual machines also have optimal configurations so make sure you use PVSCSI controllers with multiple virtual disks and have your DBA span the database across multiple virtual disks for maximum performance.

The following post shows how to do this in detail:

Splitting SQL datafiles across multiple VMDKs for optimal VM performance

If the DBA is not confident doing this, you can also just add multiple virtual disks (connected via multiple PVSCSI controllers) and create a stripe in guest (via Disk Manager) and this will also give you the benefit of multiple vdisks.

Related Articles:

1. Peak Performance vs Real World Performance

2. Enterprise Architecture & Avoiding tunnel vision

3. Microsoft Exchange 2013/2016 Jetstress Performance Testing on Nutanix Acropolis Hypervisor (AHV)

Microsoft Exchange on Nutanix Best Practice Guide

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I am pleased to announce that the Best Practice guide for Microsoft Exchange on Nutanix is released and can be found here.

For me deploying MS Exchange on Nutanix with vSphere combines best of breed application level resiliency (in the form of Exchange Database Availability Groups), infrastructure and hypervisor technologies to provide an infrastructure with not only high performance, but with industry leading scalability, no silos and very high efficiency & resiliency.

All of this leads to overall lower CAPEX/OPEX for customers.

In summary by Virtualizing MS Exchange on Nutanix, customers realize several key benefits including:

  • Ability to use a standard platform for all workloads in the datacenter, thus allowing the removal of legacy silos resulting in lower overall cost, and increased operational efficiencies.
    • An example of this is no disruption to MS Exchange users when performing Nutanix / Hypervisor or HW maintenance
  • A highly resilient , scalable and flexible MS Exchange deployment.
  • Reducing the number of Exchange Mailbox servers required to maintain 4 copies of Exchange data thanks to the combination of NDFS + DAG. (2 copies at NDFS layer / 2 copies at DAG layer)
  • Eliminate the need for large / costly refresh cycles of HW as individual nodes can be added and removed non disruptively.
  • Simplified architecture, no need for complex sizing architecture or risk of over sizing day 1, start small and scale VMs, Compute or storage if/when required.
  • No dependency of specific HW, Exchange VMs can be migrated to/from any Nutanix node and even to non Nutanix nodes.
  • Full support from Nutanix including at the Exchange, Hypervisor and Storage layers with support from Microsoft via Premier Support contracts or via TSANet.
  • Lower CAPEX/OPEX as Exchange can be combined with new or existing Nutanix/Virtualization deployment.
  • Reduced datacenter costs including Power, Cooling , Space (RU)

I hope you enjoy the Best Practice guide and look forward to hearing about your MS Exchange on Nutanix questions & experiences.

VMware Host Isolation Response in a Nutanix Environment #NoSAN

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I was recently discussing the Nutanix solution with a friend of mine and fellow VCDX, Michael Webster (@vcdxnz001) and he asked what the recommended Host Isolation Response is for Nutanix.

At this stage I must advise there is no formal recommendation, but an Official vSphere on Nutanix Best Practice guide is in the works and will be released asap.

Back to my conversation with Michael, Being that Nutanix is an IP Storage solution, my initial feeling is that Host isolation Response should be set to “Shutdown”, but I didn’t go into any more detail with Michael, so I thought it best to post a quick explanation.

This post also assumes basic knowledge of vSphere as well as the Nutanix platform, for those of you who are not familiar with Nutanix please review the following links prior to reading the remainder of this post.

About Nutanix | How Nutanix Works | 8 Strategies for a Modern Datacenter

So back on topic, in other posts I have written for IP Storage, such as (Example Architectural Decision – Host Isolation Response for IP Storage) I have concluded that “Shutdown” was the most suitable setting and recommended specifying isolation addresses of the NAS controllers.

But as Nutanix changes the game and has one virtual storage controller per ESXi host, so does this change the recommendation?

In short, No, but for those who are interested, here is why.

If we leave the default isolation address, (being the default gateway for ESXi Management), in the event the gateway is down, it will trigger an isolation response even if the rest of the network is operating fine, thus an unnecessary outage would occur.

If we configure das.isolationaddress1 & 2 with the Management IP address of any two Nutanix Controller VMs (192.168.1.x , 192.168.1.y in my below diagram) then an isolation response will only be triggered if both Nutanix Controller VMs (CVMs) are not responding, in which case, the VMs should be Shutdown as the Nutanix cluster may not be function properly with two Controllers offline concurrently as its configured by default for N+1 (or replication factor of “2” in Nutanix speak).

The below is a high level example of the above configuration.

NutanixHostIsolation

Related Articles

1. Example Architectural Decision – Host Isolation Response for a Nutanix Environment

2. Storage DRS and Nutanix – To use, or not to use, that is the question?

3. VMware HA and IP Storage