CPU Hot-Add And NUMA

Frank Denneman discusses VMware NUMA behavior when you hot-add more CPUs:

But what happens when the VM is configured with less vCPUs than the core count of the physical CPU package and CPU Hot-Add is enabled? Will there be performance impact? And the answer is no. The VPD configured for the VM fits inside a NUMA node, and thus the CPU scheduler and the NUMA scheduler optimizes memory operations. It’s all about memory locality. Let’s make use of some application workload test to determine the behavior of the VMkernel CPU scheduling.

For this test, I’ve installed DVD Store 3.0 and ran some test loads on the MS-SQL server. To determine the baseline, I’ve logged in the ESXi host via an SSH session and executed the command: sched-stats -t numa-pnode. This command shows the CPU and memory configuration of each NUMA node in the system. This screenshot shows that the system is only running the ESXi operating system. Hardly any memory is consumed. TotalMem indicates the total amount of physical memory in the NUMA node in kb. FreeMem indicates the amount of free physical memory in the NUMA node in kb.

Interesting reading.

SQL Server On VMware Guide

David Klee announces an update to VMware’s SQL Server best practices guide:

I am proud to announce that we contributed to the latest revision of the Microsoft SQL Server on VMware best practices guide, freely available at this address. This document outlines some of the common VM-level tweaks and adjustments that are made when running enterprise SQL Server VMs on VMware platforms. This guide is considered a must-read if you manage these sorts of SQL Servers, which cannot be treated as general purpose virtual machines.

This guide was recently updated for vSphere 6.5, and we consider it an absolute must for your enterprise management library!

If you manage SQL Server instances on VMware, it’s definitely worth the read.

Disabling VMware In-Guest Clock Updates

David Klee explains when VMware will update the internal clocks for VMs and shows how to disable that:

These time sync actions can move a guest’s time backwards as well as forwards. More details about this conflict of settings are found in VMware KB1189. If the host time is out of sync, such as when a BIOS battery fails, bad things can happen. This action is extremely detrimental to the state of SQL Server high availability features, such as Availability Groups and Failover Cluster Instances, which depend on the in-guest time closely aligning with the Active Directory synchronized time. This action must be explicitly disabled to ensure that these maintenance items do not trigger an unexpected failover of the SQL Server HA solution. To disable this action, perform the following tasks.

I’d imagine that the ideal would be everything being synched to a single NTP source.

Azure VM Encryption

Melissa Coates looks at different encryption methods available for Azure Virtual Machines:

Initially I opted for Storage Service Encryption due to its sheer simplicity. This is done by enabling encryption when you initially provision the storage account. After having set it up, I had proceeded onto other configuration items, one of which is setting up backups via the Azure Recovery Vault. Turns out that encrypted backups in the Recovery Vault are not (yet?) supported for VMs encrypted with Storage Service Encryption (as of Feb 2017).

Next I decided to investigate Disk Encryption because it supports encrypted backups in the Recovery Vault. It’s more complex to set up because you need a Service Principal in AAD, as well as Azure Key Vault integration. (More details on that in my next post.)

Click through for a point-by-point comparison between the two methods.

VSphere 6.5 And VNUMA

David Klee notes that vSphere 6.5 might modify vNUMA settings on you:

I appreciate their attempt to improve performance, but this presents a challenge for performance-oriented DBAs in many ways. It now changes expected behavior from the basic configuration without prompting or notifying the administrators in any way that this is happening. It also means that if I have a host cluster with a mixed server CPU topology, I could now have NUMA misalignments if a VM vMotions to another physical server that contains a different CPU configuration, which is sure to cause a performance problem.

Worse yet is that if I were to restart this VM on this new host, the hypervisor could automatically change the vNUMA configuration at boot time based on the new host hardware.

I now have a change in vNUMA inside SQL Server. My MaxDOP settings could now be wrong. I now have a change in expected query behavior. 

Definitely read the whole thing if you’re using vmWare.

Dockerizing ASP.Net Applications

Elton Stoneman shows how to package an ASP.Net web application into a Docker image:

It’s how you start to package “legacy” ASP.NET apps in Docker images, so you can run them in containers on Windows 10 and Windows Server 2016. Once you’ve packaged your app into a container image you have:

  • a central artifact which dev and ops teams can work with, which helps you transition to DevOps;

  • an app that runs the same on your laptop, on the server, on Azure, on AWS, which helps you move to the cloud;

  • an app platform which supports distributed systems, which helps you break down the monolith into microservices.

This is part one of a series, but if you read through this post, you’ll end up with a fully-functional app.

Docker On Windows Server

Elton Stoneman walks us through how to run Docker on Windows Server 2016:

There are two Windows Base images on the Docker Hub – microsoft/nanoserver andmicrosoft/windowsservercore. We’ll be using an IIS image shortly, but you should start with Nano Server just to make sure all is well – it’s a 250MB download, compared to 4GB for Server Core.

docker pull microsoft/nanoserver 

Check the output and if all is well, you can run an interactive container, firing up PowerShell in a Nano Server container:

Docker will also run on Windows 10 Pro, Enterprise, or Education editions.  That’s sad news for people who upgraded for free to Home Edition.

VMware Configuration Reports

Allen McGuire has a few Reporting Services reports that he created against vCenter Database:

So you are a DBA and you are in a virtual environment – VMware in particular.  You are curious to know the health of the VMware hosts in terms of CPU and RAM, but you really don’t know how to get the data you need and you’re not certain if the information you are asking for is entirely accurate.  Well, chances are you have access to the VMware databases themselves – if that is the case, you can create these reports based on a blog post from Jonathan Kehayias: “Querying the VMware vCenter Database (VCDB) for Performance and Configuration Information“.

I have created five reports that are based on Jonathan’s queries and you can download the RDL for the SSRS reports below – enjoy!

Click through for the reports.

Private Clouds

James Serra argues that virtualization does not by itself make for a private cloud:

Since virtualization only solves #3, a lot more should be done to create a private cloud.  Also, a cloud should also support Platform-as-a-service (PaaS) to allow for application innovation.  Fortunately there are products to add the other characteristics to give you a private cloud, such as Microsoft’s Azure Stack.  And of course you can always use a public cloud.

Read James’s post to get the full listing of what makes for a “cloud” offering.

Diagnosing Virtual Machine Cloning Issues

Jack Li walks through a few common problems when creating Azure VMs based off of captured images:

When you create VM from a captured image, the drive letters for data disks may not preserved.  For example if you have system database files on E: drive, it may get swapped to H: drive.  If this is the case, SQL Server can’t find system database files and will not start.  If the driver letter mismatch occurs on user database files, then the user databases will not recover.   After VM is created, you just need to go to disk management to change the drive letters to match your original configuration.

Read the whole thing if you’re thinking about copying your on-premise server to an Azure VM.

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