Black Friday? Nah… BrownBag Friday! Here’s the video for this weeks BrownBag:

ProfessionalVMware VCAP DCA Section 2 BrownBag from ProfessionalVMware on Vimeo.

If you like what you see… be sure to check out our other BrownBags here. If you need the full video, you can download it from the Vimeo link above.

@vRobM and I were discussing an unrelated topic when DRS and the mysterious stars came up.  (**)?  Our first instinct was this was the “special sauce” between the two all beef patties.  However after some creative KB searching we came across a formula that describes it quite well:

DRS Recommendations

To understand the stars, you need to understand where to find them and what they mean. The following is taken from the VI3 docs:

Priority for this recommendation, as a number of stars.  Five stars, the maximum, indicate a mandatory move because of a host entering maintenance mode or affinity rule violations. Other ratings denote how much the recommendation would improve the cluster’s performance; from four stars (significant improvement) to one star (slight).

So that explains what the stars indicate as far as recommendations go.  But what makes a 3 star and what makes a 4 star recommendation?

Calculating the Priority

Turns out that this isn’t exactly the special sauce we thought it was. Rather, there is some carefully reasoned out math that goes into this.  This KB article spells it out in detail, but we’ll hit the high points.  First the formula:

6 – ceil(LoadImbalanceMetric / 0.1 * sqrt(NumberOfHostsInCluster)).

There are two variables in there and only one of which is obvious, “LoadImbalanceMetric” however can be interesting:

LoadImbalanceMetric is the current host load standard deviation shown on the cluster’s Summary page of the vSphere Client.
For each host, compute the load on the host as sum(expected VM loads)) / (capacity of host). Then compute the standard deviation of the host load metric across all hosts to determine LoadImbalanceMetric.

So where does one find this standard deviation? Select your cluster, then summary and look for the following section:

In our particular case, not much to look at, as well, she is seemingly a well balanced cluster. However let’s work through the formula with the assumption that we have a 2 node cluster and a standard deviation of 0.282 (the “target” from above):

6 – ceil(0.282 / 0.1 * sqrt(2)).

What is Ceilias brother Ceil doing with my numbers?

Turns out, it is not a family of mathematicians busily flicking their abacus’.  ‘Ceil’ here, represents the Ceiling function, which I’m sure you’ve heard of before.

According to Wikipedia the Ceiling function is:

In mathematics and computer science, the floor and ceiling functions map a real number to the largest previous or the smallest following integer, respectively. More precisely, floor(x) = ⌊x⌋ is the largest integer not greater than x and ceiling(x) = ⌈x⌉ is the smallest integer not less than x.

So that works out as:

or:

6 – the smallest number not less than (0.282 / .1 * sqrt(2)) which equals 2, hence, a 2 star recommendation. (**)!

More info: Duncan Epping @ Yellow-Bricks has put together an excellent Deep-dive page for DRS, where you can get into much greater detail.

WolframAlpha to the Rescue

While this can easily be done in any random calculator (or in the heads of some folk) I used WolframAlpha to good avail.  It’s quick and gives you a graphical breakdown of the formula. Just plug in new values and go!

Summary

The recommendations and mathematical bits take place behind the scenes seamlessly.  After all, that is the magic of DRS.  However, it helps to have an understanding of the actual logic and math that goes into those recommendations so you can better understand your cluster, and better plan for new hosts and workloads.  As always drop a line in the comments or tweet to either @vRobM or myself on Twitter.

Update: Thanks for the excellent deep-dive page Duncan!

I mean it. Really. One of my pet peeves is the fellow who installs VMware server on his workstation to run his work provided Windows XP image (or some variant of Linux). The logic behind this usually goes something like:

“I needed to be able to create virtual machines and VMware Server is the only free VMware product that will let me do that.”

First, while that may have been the case in the past, it is not anymore. Second, there are a host of reasons why Server likely is not suited for your workstation workloads.

When to use VMware Server (Use Case pt 1)

I hear you asking: “Well, when do I use VMware Server?”. The answer here is that server has a few use cases. For example, if your server hardware is not otherwise on the HCL and you have a need to run VMs in a non production environment. Server makes a great choice. It also makes a great choice when you want the virtual machines to start on boot, and will be accessing them remotely. It also makes sense when doing server development and snapshots are critical.

When not to use VMware Server (Use Case pt 2)

This list may actually be a bit longer than the above. Basically, you will want to avoid VMware server if you will be:

• Managing VMs from the console
• Want to play Doom or use 3d acceleration (can be enabled in the vmx, but let’s not go there)
• Need workstation like performance
• Continued upgrades and support (http://virtualization.info/en/news/2010/05/vmware-server-to-be-discontinued-by-june-2011.html)

Basically, VMware Server is well suited for background server work loads, rather than in your face workstation like work loads. You have VMware Player for that.

Alternatives

So if you’re not supposed to use VMware Server for workstation tasks… what are you to use? In keeping with the “Free” product type requirement, there are several good alternatives:

• VMware Player 3.0
  Player 3.0 gives you the ability to create and run virtual machines and seemingly shares some of it’s code base with VMware Workstation. Meaning while they may not be feature compatible, you will still be performance compatible.
• Sun/Oracle Virtual Box
  A bit more feature rich (teleportation anyone?). Virtual box is open source and free for use as well. It also provides excellent workstation performance.

Some for-cost alternatives involve VMware Workstation or Fusion, as well as Parallels. I’d be amiss if I didn’t also tell you that if your hardware is on the HCL and you don’t mind remote access, ESXi is likely the route to go with your server workload issues.

Summary

Basically, you’ll want to use VMware Server for server workloads on hardware that is not otherwise on the VMware HCL. For everything else there is ESXi or VMware Player (or Virtualbox, etc).

The last one of these got quite a bit of mileage, so it may be worthwhile to repeat them on occasion. This week, while sitting in VMwares DSA (Deploy, Secure, Analyze) Class posting will be ‘interesting’ at best. So here it goes:

Virtu-al’s first Online VMUG was a success, with about 30-45 viewers. It’s been recorded if you missed it, and you can sign up for the next one from the site.

VMware released a bunch of the VMworld ‘08 & VMworld Europe ‘09 material for free online. Amongst these is “AD2764 – Managing VMware with PowerShell”. You knew that one was coming, didn’t you?

The 2TB problem. Virtual Geek actually did a better write up on this than the one I had sitting in my drafts folder. As with anything else he writes it’s a worthwhile read.

The VMware Coffee Talk on PowerShell happened. All and all an excellent presentation. The ‘Demo’ mode was interesting as was the remainder of the subject matter. I hope there is a follow up on some more specific topics.

VMware also release some new classes for vSphere that seem to be centered around job specific roles. Which may mean there are some interesting things to come certification wise.

Thanks for tuning in again! If you have any questions, or comments, leave me a note in the comments.

Not sure when I came across this, and how late to the game I am on it, but alas, cleaning out my Firefox tabs today I came across a deployment diagram for the Nexus 1000v on ESX4:

Some key observations of importance:

    * The version of ESX running here is ESX 4.0 (not yet released)
    * The Nexus 1000V software on the physical server acts like a line card of a modular switch, described as a VEM (virtual ethernet module)
    * The Nexus 1000V VEM is a direct replacement of the VMWare vSwitch function
    * The Nexus 1000V VSM (virtual supervisor module) acts like the supervisor engine of a modular switch
    * One Nexus 1000V VSM instance manages a single ESX cluster of up to 64 physical servers
    * The form factor of Nexus 1000V VSM can be a physical appliance or a virtual machine
    * The network administrator manages the Cisco Nexus 1000V (from the VSM) as a single distributed virtual switch for the entire ESX cluster
    * Each virtual machine connects to its own Virtual Ethernet (vEthernet) port on the Nexus 1000V providing the network administrator traffic visibility and policy control on a per virtual machine basis.  Virtual machines can now be managed like physical servers in terms of their network connectivity.

Original post here.

So the big news last week was that VMware decided it’s time to rename VMware Virtual Infrastructure (or VI as the peeps on the street are calling it these days) to VMware vSphere. The current version seems to be staying on the VI title and the next version will move to this odd naming structure.

So far they’ve renamed a LOT of their products, Virtual Center became vCenter Server, VDI became VMware View, and many of the other DC level products moved into the VMware vCenter group.

So far some of the theories on why oh why VMware decided to confuse us all with renaming everything (some marketing itch no doubt) seem to surround brand protection and separating the name from other vendors now in the same space (Hyper-V and Hypervisor for example)

Pretty much everyone has blogged about it so far, so we’re the last on the boat, but Cody’s not here and I’m getting old.

Patrick