Stretched Clusters: Use Cases and Challenges Part I – HA
Posted by Harley Stagner
I have been hearing a lot of interest from my clients lately about stretched vSphere clusters. I can certainly see the appeal from a simplicity standpoint. At least on the surface. Let’s take a look at the perceived benefits, risks, and the reality of stretched vSphere clusters today.
First, let’s define what I mean by a stretched vSphere cluster. I am talking about a vSphere (HA / DRS) cluster where some hosts exist in one physical datacenter and some hosts exist in another physical datacenter. These datacenters can be geographically separated or even on the same campus. Some of the challenges will be the same regardless of the geographic location.
To keep things simple, let’s look at a scenario where the cluster is stretched across two different datacenters on the same campus. This is a scenario that I see attempted quite often.
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Back to the Basics with Virtualization Capacity Planning
Posted by Harley Stagner
To be sure, there are plenty of new features to get excited about in vSphere 5.0. VMware has come a long way since 2002, when I first started using the technology. Often in the technology world, practitioners get excited about learning and implementing new technology without planning properly. They want to implement as fast as possible to bring about the benefits and innovation that the new technology has to offer. I believe that we have all been guilty of this at one point. So, this post is to remind all technology practitioners to take a step back and think about proper planning when implementing new technology projects. One of the basic tasks that should be done at the beginning of any virtualization design is capacity planning.
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Virtualization Deployment Automation with vSphere 5
Posted by Harley Stagner
I recently spoke at a lunch and learn event about “Security in a Virtualized World”. If one thing was made abundantly clear during the discussion, it was the fact that securing a virtual infrastructure is more complicated than securing a physical infrastructure. There are many moving parts to consider along with the hypervisor itself. For many years, I have been discussing the need for automation with my clients. It makes the infrastructure much easier to manage and from a security standpoint it helps to ensure that build policies are consistent for all of the virtual hosts in the infrastructure.
There have always been tools to automate a vSphere infrastructure ranging from Perl scripts to PowerCLI. With the release of vSphere 5 automation is becoming more and more a reality. When you think about automating a VMware infrastructure, you may think about writing scripts to perform certain tasks or spending hours on the “perfect” ESX build that can be deployed through automation. Scripts are still available and in some cases necessary for automation. However, with vSphere 5 we are beginning to see an “automation-friendly” environment built into the management tools that are given to us from VMware.
ESXi: Built for Automation
One of the most important aspects of maintaining a consistent environment starts with the hypervisor deployment itself.
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vSphere 5 Profile-Driven Storage: Get VM Placement Right the First Time
Posted by Harley Stagner
We all get in a hurry. When we get in a hurry we make mistakes. The following scenario has been played out plenty of times in a virtual infrastructure.
- VM Administrator gets a request for a new VM to be deployed ASAP, which usually means yesterday.
- VM Administrator looks through multiple datastores to determine a datastore with a sufficient amount of capacity.
- VM Administrator picks the datastore and deploys the VM.
What if this particular VM was a database server and the log volume needed to be provisioned on a RAID1/10 datastore. Hopefully the datastores are named with the RAID level in the naming convention. But, what if they are not? Even if they are, it can be very tedious to wade through multiple datastores to find an appropriate datastore that meets both capacity and performance requirements. What if there was a way to “tag” certain datastores with characteristics that are meaningful to the VM administrator? That’s where the new “Profile-Driven Storage” feature comes in with vSphere 5.
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vSphere 5 High Availability: Bring on the Blades
Posted by Harley Stagner
vSphere 5 has many new and exciting features. This post will concentrate on High Availability(HA) and how it affects blade designs. While HA is certainly not new, it has been rewritten from the ground up to be more scalable and flexible than ever. The old HA software was based on Automated Availability Manager (AAM) licensed from Legato. This is why HA had its own set of binaries and log files.
One of the problems with this “now legacy” software was the method it used to track the availability of host resources. HA prior to vSphere 5 used the concept of primary nodes. There were a maximum of (5) primary nodes per HA cluster. These nodes were chosen by an election process at boot time. The (5) primary nodes kept track of the cluster state so that when an HA failover occurred, the virtual machines could restart on an available host in the cluster. Without the primary nodes, there was no visibility into the cluster state. So, if all (5) primary nodes failed, HA could not function.
This was not usually an issue in rackmount infrastructures. However, it posed some challenges in a blade infrastructure where a chassis failure can cause multiple blades to fail. Blade environments should typically have at least two chassis for failover reasons. If there was only a single chassis providing resources for an HA cluster, that single chassis failure could cause an entire cluster outage. You’ll seen in the diagram below that just because multiple chassis are used does not mean that the entire HA cluster is protected.
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A Structured Virtual Infrastructure Part I: Physical Infrastructure
Posted by Harley Stagner
Server virtualization is infectious. It is a technology that tends to take off in record pace in IT organizations that have adopted it as part of their infrastructure. It has been my experience that organizations fall into one of two broad categories when it comes to their virtualization initiatives. They either look at server virtualization as a “Strategic Initiative” or they use server virtualization as a “Tactical Tool.” Let’s explore these categories and then I’ll discuss some infrastructure options for a structured virtual infrastructure.
Server Virtualization as a “Tactical Tool”
I have seen this in many organizations. The IT group needed to test a new application or needed to spin up a new server quickly. What’s the quickest way to spin up a new server? Server virtualization, of course. So, here is how I see many infrastructures get started:
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End to end virtual security with the Cisco Nexus VSG
Posted by Harley Stagner
So I’ve been spending a lot of time in our lab with the Cisco Nexus Virtual Security Gateway. I have come to the conclusion that it rocks! Finally, the virtual infrastructure is no longer treated as a second class citizen when it comes to securing network traffic between virtual machines. We are at a point now with the Cisco VSG that we can have robust Cisco infrastructure, including security, from the upstream physical network to the virtual network.
