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I just woke up in an extremely warm Vietnam and noticed it is that time of the year again. I am hoping to end up somewhere at the top of the list again, but I realize like no one else that this is not a given. The competition is huge and some really stood out this year. There are three in particular that stood out in my opinion which for sure made my Top list: Cormac Hogan, William Lam and Derek Seaman. All three did something different than most bloggers do. They bring unique content, a unique perspective and showed dedication / perseverance. I am expecting all three to be in the top of the list for sure.

2013 was a crazy year… I joined a new team and am working on an exciting new product at VMware, which I unfortunately cannot talk about yet. We saw the beta release of Virtual SAN and that resulted in many many articles. I was fortunate enough to be selected to present at both VMworld EMEA and US, and presented at various VMUGs but the two which particularly stood out were Italy and Denmark as I had not been there before. The busiest blogging day of the year was August 27th with over 13k views.

I guess something exciting to mention is that I started working on a new book, of course somehow Eric Sloof managed to notice if first and scooped the news. Will take a while before it is released but the title will be: Essential Virtual SAN. The rough cuts should be online soon as well. Happy to be working with Cormac Hogan on this, I couldn’t think of anyone else who would be better fitted to write a book on the topic of VSAN with.

Something worth noting as well, the top referring sites: twitter, VMware VMTN Community, facebook, Eric Siebert’s VLP and blogs.vmware.com. In that order, and it makes you realize how important social media is today. Whether it is twitter or a community forum… it can drive a lot of traffic when used in the right way!

Thanks again to Eric Siebert who spends a MASSIVE amount of time going through the voting, filtering out discrepancies and making sure it all is done in a fair manner! Make sure to bookmark his website, add it to your RSS reader and follow him on twitter. So what are you waiting for, head on over and take the survey!

Don’t create a Frankencluster just because you can…

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In the last couple of weeks I have had various discussions around creating imbalanced clusters. Imbalanced from either CPU, memory and even a storage point of view. This typically comes up in discussions where either someone wants to bring larger scale to their cluster and they want to add hosts with more resources of any of the before mentioned types. Or also when licensing costs need to be limited and people want to restrict certain VMs to run a specific set of hosts. Something that comes up often when people are starting to look at virtualizing Oracle. (Andrew Mitchell published this excellent article on the topic of Oracle Licensing and soft vs hard partitioning which is worth reading!)

Why am I not a fan of imbalanced clusters when it comes to compute or storage resources? Why am I not a fan of crippling your environment purposely to ensure your VMs will only run on a subset of vSphere hosts? The reason is simple, the problems I have seen and experienced and the inefficiency in certain scenarios. Lets look at some examples:

Lets assume I have 4 hosts with each 128GB of memory. I need more memory in my cluster and I add a host with 256GB of memory. Now you just went from 512Gb to 768GB which is a huge increase. However, this is only true when you don’t do any form of admission control and resource management. When you do proper resource management or admission control than you would need to make sure that all of your virtual machines can run in the case of a failure, and preferably run with equal performance before and after the failure has occured. If you added 256GB of memory and this is being used and that host containing 256GB goes down your virtual machines could potentially be impacted. They might not restart, and if they restart they may not get the same amount of resources as they received before the failure. This scenario also applies to CPU, if you create an imbalance .

Another one I encountered recently was presenting a LUN to a limited set of hosts, in this case a LUN was only presented to 2 hosts out of the 20 hosts in that cluster… Guess what, when those two hosts die… so do your VMs. Not optimal right when they are running an Oracle database for instance. On top of that I have seen people pitching a VSAN cluster of 16 nodes with only 3 hosts contributing storage. Yes you can do that, but again… when things go bad, they will go horribly bad. Just imagine 1 host fails, how will you rebuild your components that were impacted? What is the performance impact? Very difficult to predict how it will impact your workload, so just keep it simple. Sure there is a cost overhead associated with separating workloads and creating dedicated clusters, but it will be easier to manage and more predictable in failure scenarios.

I guess in summary: If you want predictability in terms of availability and recoverability of your virtual machines go for a balanced environment, don’t create a Frankencluster!

What is Virtual SAN really about?

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When talking about Virtual SAN you hear a lot of people talking about the benefits, what Virtual SAN is essentially about. You see the same with various other so-called Software Defined Storage solutions. People typically, when talking about these solutions, talk about things like “enabling within 2 clicks”… Or maybe about how easy it is to scale out, or scale-up for that matter. How much performance you have because of the way they use flash drives. Or about some of the advanced data services they offer.

While all of these are important, when it comes to Virtual SAN I don’t think that is the true strength. Sure, it is great to be able to provide a well performing easy to install scale-out storage solution… but the true strength in my opinion is: Policy Based Management & Integration. After having worked with VSAN for months, that is probably what stood out the most… policy based management

What does this deep integration and what do these policies allow you to do?

  • It provides the ability to specify both Performance and Availability characteristics using the UI (Web Client) or through the API.
    • Number of replicas
    • Stripe width
    • Cache reservations
    • Space reservations
  • It allows you to apply policies to your workload in an easy way through the UI (or API).
  • It provides the ability to do this in a granular way, per VMDK and not per datastore.
  • To a group of VMs or even all VMs in a programmatic way when needed.

Over the last couple of months I have played extensively with this feature of VSAN and vCenter, and in my opinion it is by far the biggest benefit of a hypervisor-converged storage solution. Deep integration with the platform, exposed in a simplistic VM-centric way through the Web Client and/or the vSphere APIs.

vSphere Availability Survey, please help out!

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Just received the below from the vSphere Availability team. It takes a couple of minutes to fill out and it helps the vSphere Availability team to set priorities correctly for upcoming releases, yes indeed based on your answers!

— copy / paste —

The Availability team (that brings to you products such as vSphere HA, FT etc.) would like to get your input on how you use our products today and your projected needs. The survey has mainly multiple choice questions, and will take 10-15 minutes to complete. Your feedback is invaluable in helping us tailor our development efforts towards valuable enhancements. So, thank you!

Here’s the link to the survey: http://tinyurl.com/vmwavailability

Virtual SAN (related) PEX Updates

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I am at VMware Partner Exchange this week and there and figured I would share some of the Virtual SAN related updates.

  • 6th of March their is an online Virtual SAN event with Pat Gelsinger, Ben Fathi and John Gilmartin… Make sure to register for it!
  • Ben Fathi (VMware CTO) stated that VSAN will be GA in Q1, more news in the upcoming weeks
  • Maximum cluster size has been increased from 8 (beta) to 16 according to Ben Fathi, VMware VSAN engineering team is ahead of schedule!
  • VSAN has linear scalability, close to a million IOPS with 16 hosts in a cluster (100% read, 4K blocks). Mixed IOPS close to half a million. All of this with less than 10% CPU/Memory overhead. That is impressive if you ask me. Yeah yeah I know, numbers like these are just a part of the overall story… still it is nice to see that this kind of performance numbers can be achieved with VSAN.
  • I noticed a tweet Chetan Venkatesh and it looks like Atlantis ILIO USX (in memory storage solution) has been tested on top of VSAN and they were capable of hitting 120K IOPS using 3 hosts, WOW. There is a white paper on this topic to be found here, interesting read.
  • It was also reinstated that customers who sign up and download the beta will get a 20% discount on the first purchase of 10 VSAN licenses or more!
  • Several hardware vendors announced support for VSAN, a nice short summary by Alberto to be found here.

vSphere HA and VMs per Datastore limit!

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I felt I would need to get this out there, as it is not something many seem to be aware off . More and more people are starting to use storage solutions which offer 1 large shared datastore, examples are solutions like Virtual SAN, Tintri and Nutanix. I have seen various folks saying: unlimited number of VMs per datastore, but of course there are limits to everything! If you are planning to build a big cluster (HA enabled), keep in mind that per cluster your limit for a datastore is 2048 powered-on virtual machines! Say what? Yes that is right, per cluster you are limited to 2048 powered-on VMs on a single datastore. This is documented in the Max Config Guide of both vSphere 5.5 and vSphere 5.1. Please note it says datastore and not VMFS or NFS explicitly, this applies to both!

The reason for this today is the vSphere HA poweron list. I described that list in this article, in short: this list keeps track of the power-state of your virtual machines If you need more VMs in your cluster than 2048 you will need to create multiple datastores for now. (More details in the blog post) Do note that this is a known limitation and I have been told that the engineering team is researching a solution to this problem. Hopefully it will be in one of the upcoming releases.

Awesome VSAN contest results

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Every once in a while I have someone asking me how about VSAN scale? Typically the question is triggered by a conversation had with another storage vendor and either a misunderstanding or pure FUD that was spread. It is nice to see some of our beta testers showing the possibilities with VSAN. How about the result of the Miami VMUG? These guys managed to get their hands on 3 awesome Dell R720xd hosts and found someone willing to host them. Then they started building, and it didn’t take them long to figure out what the limit was on a 3 node cluster… They managed to run 2250 virtual machines on 3 hosts. Yes, that is indeed more than two thousand virtual machines.

Thanks Miami VMUG for going all out.