VMware’s VMTools package has some options for synchronizing the in-guest clock with the time of the ESXi host. By default, these are set to disabled, and under most circumstances, the hypervisor follows these settings and everything is fine. However, several situations exist where the hypervisor will reset the in-guest time, even though the VMTools setting…
Category: Virtualization
VMware vSphere 6.5 breaks your SQL Server vNUMA settings
VMware’s latest release of the vSphere virtualization suite, version 6.5, changes how they handle vNUMA presentation to a virtual machine, and there’s a high likelihood that it will break your virtualized SQL Server vNUMA configuration and lead to unexpected changes in behavior. It might even slow down your SQL Servers. Here’s what you need to…
Load Testing Results Might Not Be What You Think
Bottlenecks in your testing tools, infrastructure, or methodology might just hurt your load test results, and the results can skew your metrics. For example… A few weeks ago we were running an iperf load test to see what improvements (if any) could be made to the configuration of a Windows Server networking stack. Setting up iperf…
VMware CPU Co-Stop and SQL Server Performance (continued)
A number of you sent me some excellent questions about this topic, and my favorite asked me for the query that you can use to get this information DIRECTLY from the VMware vCenter database. SO… here you go! Just plug in your VM name (which might differ from your FQDN name). Feel free to modify…
VMware CPU Co-Stop and SQL Server Performance
Not too many people know about the intricacies of virtualization CPU scheduling and its impact on the performance of the VMs, so application owners out there – listen up! I’ve written about Ready Time (VMware ESXi) / Wait Time Per Dispatch (Microsoft Hyper-V) in the past, but a different challenge arises with VMs that have large vCPU count…
Q&A: Multiple SQL Server Instances on a VM
I recently received a great question through email. It was whether or not it is a good idea to have multiple SQL Server instances on a single VM. This is a fun question and I thought I’d answer it here. The answer is the ubiquitous DBA answer – “It Depends“. Both pros and cons exist…
Summon Blue Screens of Death (for testing purposes only, of course)
Today I had a need to manually trigger and sustain a Blue Screen of Death (BSOD) inside a Windows Server VM. The goal was to be able to trigger a BSOD so that I could work on the detection of powered on but failed VMs inside a server environment. All major hypervisors have this feature…
Availability Group WSFC Failovers During VM Movement
If you experience a WSFC failover during a VMware vMotion / Hyper-V Live Migration with your virtualized SQL Servers when using Availability Groups, you might have server and/or networking hardware that takes a bit longer than usual to handle the network port failover. This can lead to short unexpected outages in your application during the…
Retrofit a VM with the VMware Paravirtual SCSI Driver
For those of you with your mission-critical servers already virtualized on a VMware-based virtual infrastructure, are you using the VMware Paravirtual SCSI driver to boost your I/O performance by an average of 12%? I use it for all of my I/O intensive virtual machines, including SQL Server and Oracle VMs, and you should too! By…
SQL Server Virtual Machine vNUMA Sizing
A wonderful gentleman who attended my SQL PASS Summit session this year recently emailed me and asked me a great question about optimal setup for SQL Server virtual machine vCPU and vNUMA configurations. I thought about the question and realized that while the session went into a light level of detail, I can go much…