Jan 182016

emblem-questionI 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 to this configuration. I’ll outline them both for you.


  • If you are licensing based on the VM rather than the physical CPU cores, you can potentially minimize your licensing spend.
  • You have fewer operating systems to manage and patch.
  • You might need to isolate an application to its own instance for security purposes, but the resource demands are not great enough to necessitate another VM.
  • You might need to mix different SQL Server versions to support different applications, but do not have available licensing for additional VMs.
  • You can patch and restart individual SQL Server instances independent of the others as needed, which can reduce the downtime that is usually associated with one large consolidated instance with many applications connected to it.
  • You have more VMs to manage and monitor, which means a greater level of involvement for daily operational activities.


  • You now have to manage resource consumption at both the VM and SQL Server instance levels. For example, if you have two instances on a given VM, one SQL Server instance could start to consume all of the available CPU on the VM, and can cause the other instance to take a background stance and cause performance problems as a result. To manage this in the long term, some sort of action must be taken, such as CPU affinity, resource governor, etc. This action goes along with the management of the VM-level resource consumption, such as vCPU count, host-level CPU contention, memory management and allocations, resource throttling and prioritization, etc.
  • Smaller VMs are more flexible and are easier to migrate to another host or even upgrade.
  • You might need a larger VM to properly power all of the instances, which could possibly negate the vCPU licensing savings from the consolidation exercise.
  • You have more flexible outage windows. If Windows were to need to be patched, or even worse, fail – all instances are down unless you have an HA solution in place for each instance. Scheduling planned outages with multiple business groups, multiple applications, and multiple instances on the same OSE can be a nightmare, and sometimes not even possible.
  • Security is improved because one support request might need OS-level access. If they have access to the OS but only one instance, they can still see the files of other instances and potentially cause problems.
  • Depending on your workload, you might end up with resource contention inside the VM itself. It usually manifests in things such as disk queuing contention within Windows, and can exhibit signs of higher disk latency and slower SQL Server performance as a result.

emblem-noticeI am personally partial to having just one instance per VM, as long as the situation allows for it. The resource management area between SQL Server and Windows allows me to manage the overall resource consumption at the VM level, and en mass, managing at this layer rather than multiple layers is usually preferable. I claim that the extra overhead of managing more VMs is worth the resource management flexibility.

Weight your options carefully and select the right path for your installations. Both options are certainly workable, depending on your environment and circumstance.

 Posted by at 10:33 am
Jan 052016

Next Wednesday, January 13th, at 1pm Eastern the PASS Virtualization Virtual Chapter will be holding an open questions and answers session on anything related to SQL Server virtualization, with me as your host! Send over your questions to either Tom Norman (VC lead), or over to me and we’ll get them answered for you! Any SQL Server virtualization question is welcomed in this no-holds-barred open session. We’ve had a blast with these in the past, and look forward to answering all of your questions!

RSVP for this free webinar here!

Dec 172015

Poor storage performance continues to be the largest pain point with enterprise Database Administrators in today’s virtual world. However, it is not the only challenge to the enterprise. The cost of the infrastructure pales in comparison to the licensing costs of the database platform. These challenges impact not only the DBAs, but also the financial side of the business. The business is constantly seeking ways to reduce the financial strain of the IT infrastructure, looking for ways to cut operational costs any way possible.

Decoupling storage acceleration from the storage layer can improve performance, but can also introduce some benefits not immediately obvious to the technologists in the organization.

What if the business could improve performance and reduce your licensing costs at the same time? 

PernixLogo_smHeraflux is proud to announce a new whitepaper developed jointly with PernixData to discuss and demonstrate the power of the FVP product in reducing the licensing footprint of enterprise SQL Server deployments.

Download this new whitepaper here.

Dec 022015

CaptureOn Tuesday, December 15th, Bala Narasimhan and I are presenting a webinar where we will walk through real-world examples that show how to potentially save 20% or more on your SQL Server deployment.

We’ll discuss how to tackle this pressing SQL Server challenge. More specifically, we will discuss how to:

  • Optimally size your infrastructure for virtual database performance
  • Potentially reduce SQL Server Enterprise core-based host licensing footprint
  • Optimize database performance through storage acceleration

Come join us for an exciting discussion on this ubiquitous topic! Register today for this free webinar here.

Nov 112015

help-browser-2Earlier this week I received a great question from a friend, and read something like this.

Hi David,
I usually recommend people to install SQL Server on VM and I argument it by saying that it would make any future hardware migration easier.
However, I just think if company purchases new hardware and going for SQL 2014 they won’t upgrade their hardware for at least 5-6 years. At this time there will be a necessity to go to the fresh version of SQL. So, my argument does not work anymore.
Even with very low overhead, VM adds more complexity to SQL Server environment, by adding “moving” pieces which can break.
How would you justify a case of having VM when client plans to have a model “one machine – one SQL Server”?

That’s a wonderful question, and I get asked this all the time.

I can justify the desire for virtualization in the scenario you described. There are a number of reasons to consider virtualization given those constraints.

number-1-iconHardware independence is still a great reason to virtualize, especially for disaster recovery purposes. Simply having the ability to replicate the VM itself to another datacenter and be able to restart the VM without requiring the exact same hardware underneath is very beneficial. It simplifies DR to an (almost) trivial task. You can also use last generation hardware (or even a public cloud host) for your DR site infrastructure, and it will work beautifully!

number-2-iconRisk minimization for high availability is huge as well. If that physical server were to fail, you’re at the mercy of whatever support policy you have with your hardware vendor, which can take hours or even days. Even if you are using SQL Server HA, you now have a situation where you could now be presented with a single point of failure. With virtualization and the right datacenter architecture, in the event of host hardware failure, that VM is down for about four minutes, give or take, while it restarts on a remaining host. That fact alone is why I say virtualize without hesitation, even if you’re leveraging physical clustering or AGs for robust SQL Server-level high availability.

number-3-iconHardware portability still plays well. Even if you plan for 5-6y from the physical server, how fast are the database demands on the hardware growing? Will you outgrow that physical server before then? What if you need more RAM four years from now and it’s cheaper to buy a new server with more RAM than simply upgrade your current server? The same goes for CPU cores, clock speed, etc.

face-coolEven with virtualization’s low overhead, it IS another layer in the infrastructure. But, managed correctly, I claim that the benefits described above outweigh the added layer drawbacks, as long as the admins in your environment are comfortable managing large and resource intensive VMs. Virtualize everything!

 Posted by at 10:25 am
Nov 092015

PASS_2015_240x400Last week’s PASS Summit conference in Seattle, WA was incredible (as always). It’s my favorite tech event of the year, and I’ll never miss it. The SQL Server community is one of the strongest (and arguably the most tight-knit) technical community in the world, and the #sqlfamily comes together every year at this event. It’s a whirlwind of technical education and networking events.

The highlights of the week were immersing in that sense of a family reunion that we get at this event every year, plus getting the thrill of presenting the content that I love in front of a large and eager audience.

To start the week, Argenis Fernandez, Jimmy May, and myself gave an all-day preconference training session titled ‘The Complete Primer to SQL Server Virtualization‘ to a room of 90 folks. We had a blast! For those of you who did not receive my email with the attachments as promised, email me. Some emails bounced back.

Pike's Market - by Matt Slocum

Pike’s Market – by Matt Slocum

I also had a panel session called ‘Is Independent Consulting for Me?‘ on Friday morning with John Sterrett, Brian Moran, and Ben DeBow. We packed the room and had some fantastic questions from the attendees! Feel free to contact any of us for our experiences if you are seriously considering taking the plunge to go independent.

To round out the sessions on Friday, Ed Leighton-Dick and I gave a session called ‘How to Build a Virtual Home Lab‘ where we talk about the various methods you can use to build a test lab – from the smallest and least expensive local deployments to the crazy home lab that I have at my place. Let us know if you have any questions! We love to help empower people to learn in the convenience of their home at their own pace on the topics that they want to know more about (and we’re hardware geeks to boot!).

Friday night was a blast as well. To wrap up the week, we coordinated a small get together of folks for go-kart racing at K1 Speed Seattle.

K1 Speed Go Karting

K1 Speed Go Karting

Saturday a few of us also got out and explored Seattle with the Seattle Underground tour and then a trip to the Living Computer Museum. Take the time to see the sites while you’re in Seattle! It’s an amazing town!

Pike's Market Welcomes PASS

Pike’s Market Welcomes PASS

To the PASS organizers and volunteers: outstanding job! You all did another incredible job with the conference. You knocked it out of the park this year, and we look forward to seeing what you can do in 2016.

To the attendees: if you think you’re going to catch up on sleep at this conference, you’re not doing it right. the after-hours networking opportunities at this event are limitless, and the friendships will last a lifetime. Take the time to get to know folks outside of your comfort zone, because expanding your network is part of the #sqlfamily magic! Find the folks in person that you’ve been following on Twitter or reading their technical blog posts for years. Get to know them. Network with the vendors in the expo hall. Chat with random folks in the hallways. The discussions are always priceless!

Group Photo by Eve Acosta

Group Photo by Eve Acosta – Sumeet Bansal, Andy Yun, and Jon Shields

Build your own traditions while you’re here. The Tap House for end-of-day drinks seems to be a favorite of many. My favorite thing to do is to get up early on Saturday morning and go to Lowell’s in Pike’s Place Market to eat a quiet breakfast overlooking the waterfront. You get to see the city wake up, all while relaxing quietly with a cup of tea and out of the hustle of the city.

Seattle Waterfront

Seattle Waterfront

Just remember – there are no goodbye’s. I’ll see you all at the PASS Summit next year (or hopefully sooner)!

FYI – Don’t fly home Friday afternoon next year! Stick around for the afternoon sessions. They are worth it! Plus, for next year’s PASS Summit, I’m planning a new special event for Friday night for the group, so stay tuned!