Yellow Bricks

by Duncan Epping

virtual san

Non-Uniform configurations for VSAN clusters

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I have been receiving various questions around support for non-uniform configurations in VSAN environments (sometimes also referred to as “unbalanced” configurations) . I was a bit surprised by it to be honest as personally I am not a big fan of non-uniform configurations to begin with. First, with “non-uniform” I am referring to different hardware configurations. In other words you have four hosts with 400GB Intel s3700 flash and one host with 200GB Intel s3500 flash. The question was if this is an acceptable configuration if the overall flash capacity still meets the recommended practice of 10% of used capacity.

Although technically speaking this configuration will work and is supported, from an operational and user experience perspective you need to ask yourself if this is a desired scenario. I have seen people doing these type of constructions out in the field as well with “flash caching” solutions and believe me when I say that the result were very mixed. The problem is that when you have a non-uniform configuration your predictability of performance will be impacted. As you can imagine cutting your flash capacity in half on a host could impact the cache hit ratio for that particular host. Also using a different type of flash will change your results / experience more then likely. On top of that, imagine you need to do maintenance on your hosts, it could be that the “non-uniform” host will have different procedures for whatever maintenance you are doing… it just complicates things unnecessarily.

So again, although this is supported and will work from a technical perspective it is not something I would recommend from an operational and user experience point of view.

What is coming for vSphere and VSAN? VMworld reveals…

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I’ve been prepping a presentation for upcoming VMUGs, but wanted to also share this with my readers. The session is all about vSphere futures, what is coming soon? Before anyone says I am breaking NDA, I’ve harvested all of this info from public VMworld sessions. Except for the VSAN details, those were announced to the press at VMworld EMEA. Lets start with Virtual SAN…

The Virtual SAN details were posted in this Computer Weekly article, and by the looks of it they interviewed VMware’s CEO Pat Gelsinger and Alberto Farronato from the VSAN product team. So what is coming soon?

  • All Flash Virtual SAN support
    Considering the price of MLC has lowered to roughly the same price as SAS HDDs per GB I think this is a great new feature to have. Being able to build all-flash configurations at the price point of a regular configuration, and with probably many supported configurations is a huge advantage of VSAN. I would expect VSAN to support various types of flash as the “capacity” layer, so this is an architects dream… designing your own all-flash storage system!
  • Virsto integration
    I played with Virsto when it was just released and was impressed by the performance and the scalability. Functions that were part of Virst such as snapshots and clones these have been built into VSAN and it will bring VSAN to the next level!
  • JBOD support
    Something many have requested, and primarily to be able to use VSAN in Blade environments… Well with the JBOD support announced this will be a lot easier. I don’t know the exact details, but just the “JBOD” part got me excited.
  • 64 host VSAN cluster support
    VSAN doesn’t scale? Here you go,

That is a nice list by itself, and I am sure there is plenty more for VSAN. At VMworld for instance Wade Holmes also spoke about support for disk controller based encryption for instance. Cool right?! So what about vSphere? Considering even the version number was dropped during the keynote and it hints at a major release you would expect some big functionality to be introduced. Once again, all the stuff below is harvested from various public VMworld sessions:

  • VMFork aka Project Fargo – discussed here…
  • Increased scale!
    • 64 host HA/DRS cluster, I know a handful of customers who asked for 64 host clusters, so here it is guys… or better said: soon you will have it!
  • SMP vCPU FT – up to 4 vCPU support
    • I like FT from an innovation point of view, but it isn’t a feature I would personally use too much as I feel “fault tolerance” from an app perspective needs to be solved by the app. Now, I do realize that there are MANY legacy applications out there, and if you have a scale-up application which needs to be highly available then SMP FT is very useful. Do note that with this release the architecture of FT has changed. For instance you used to share the same “VMDK” for both primary and secondary, but that is no longer the case.
  • vMotion across anything
    • vMotion across vCenter instances
    • vMotion across Distributed Switch
    • vMotion across very large distance, support up to 100ms latency
    • vMotion to vCloud Air datacenter
  • Introduction of Virtual Datacenter concept in vCenter
    • Enhance “policy driven” experience within vCenter. Virtual Datacenter aggregates compute clusters, storage clusters, networks, and policies!
  • Content Library
    • Content Library provides storage and versioning of files including VM templates, ISOs, and OVFs.
      Includes powerful publish and subscribe features to replicate content
      Backed by vSphere Datastores or NFS
  • Web Client performance / enhancement
    • Recent tasks pane drops to the bottom instead of on the right
    • Performance vastly improved
    • Menus flattened
  • DRS placement “network aware”
    • Hosts with high network contention can show low CPU and memory usage, DRS will look for more VM placements
    • Provide network bandwidth reservation for VMs and migrate VMs in response to reservation violations!
  • vSphere HA component protection
    • Helps when hitting “all paths down” situations by allowing HA to take action on impacted virtual machines
  • Virtual Volumes, bringing the VSAN “policy goodness” to traditional storage systems

Of course there is more, but these are the ones that were discussed at VMworld… for the remainder you will have to wait until the next version of vSphere is released, or you can also sign up for the beta still I believe!

Queue Depth info in the VSAN HCL!

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I just noticed there has been an update to the VSAN HCL. When I now do a search for a disk controller (vmwa.re/vsanhcl) it immediately shows the queue depth of the controller. This will make life a lot easier, especially for those who prefer to build their own Virtual SAN node instead of using a Ready Node configuration. Although it is just a minor detail it is useful to know, and will definitely make life a lot easier when configuring your component built Virtual SAN nodes.

VSAN with AHCI controller with vSphere 5.5 U2

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I’ve been following a thread on the community forums closely around the AHCI disk controller. This disk controller is an on-board disk controller which caused some problems when used in conjunction with VSAN because of a driver problem. Note that this disk controller is not on the HCL and is not recommend for use in a production environment or ANY environment where reasonable performance is expected and endurance / availability is key. Many homelabbers used this controller however and I am happy to say that it was reported by Philzy that this fix mentioned in KB 2079729 appears to have solved the issues experienced.

For all those wanting to use VSAN in their homelabs… Game on!

EVO:RAIL vs VSAN Ready Node vs Component based

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EVO:RAIL is awesome! That is typically what I hear from customers when pitching the EVO:RAIL play and showing the config and management demo. Customers are all over it I can tell you. They love the ease of deployment, management, procurement and support… Now, every now and then this geeky person pops up and say: but euuhm, I want more disks and I want to scale per node and all of my configuration stuff is scripted. How will that work with EVO:RAIL?

This is when I show them this slide:

It is a very very valid question to be honest. It is something which I, as a geek, would ask as well. How can I tweak the configuration so that it meets my requirements, and can I just use my own deployment mechanism? Sure you can, but not necessarily with EVO:RAIL. Keep in mind that EVO:RAIL is build using trusted VMware technology like VMware vSphere, vCenter Server, Virtual SAN and Log Insight. Although the EVO:RAIL engine (configuration and management interface) cannot be downloaded separately the components can be. We very much realize that EVO:RAIL may not be a fit for all customers and that is exactly why VMware offers choice as the slide above shows.

If you are a geek, love digging through hardware compatibility lists, like to configure your own servers part by part and have absolute maximum flexibility then option 1 is your best choice. Using the “Component Based” approach you can select your own: Server (vSphere HCL) and then from the VSAN HCL pick your components like the disk controller, SSD and magnetic drives. You get to pick how many drives, which type of flash, how much memory, how many cores per CPU… you name it. Note though, that it does mean you will need to do research to find out which components work well together, what kind of performance you can expect from disk controller x, y or z. But it is doable, many customers have already done this and it will allow you to design to your specific needs. Do note, you will need to configure it yourself and purchase licenses / support.

If you prefer a simpler approach, but still a certain level of flexibility then the “Virtual SAN Ready Node” approach is definitely a great option. It provides you a selection of around 40 different OEM configurations which have been validated by both the OEMs and VMware. Note though that these configurations are typically based on VM configuration profiles and IO profiles. This is mentioned in the Virtual SAN Ready Node list, there are low / medium / high configurations and also two different VDI configurations for each of the different server platforms. If you prefer a pre-validated solution, but need some flexibility then this is the way to go. Again, you will need to install/configure it yourself and purchase licenses / support, but it definitely easier than “component based”.

The third option is “VMware EVO:RAIL“. EVO:RAIL is at the far right of the slider –> Maximum Ease of Use. EVO:RAIL is pre-built on a qualified platform. This means that it comes pre-installed, and can be configured within 15 minutes. It has an easy / simple management interface that allows for easy patching/updating, simple VM creation and management, and even easier automatic scale-out (a couple of clicks). On top of that, it is sold as a single SKU (all licenses and support included) and all support will go through 1 channel. No more being pointed from one vendor to the other, no you contact that single vendor for both support of software as for hardware… Maximum Ease of Use as I said. If this is what you are looking for, EVO:RAIL is what you need.

As you see, when it comes to scale-out server SAN / hyper(visor) converged solutions… VMware offers you maximum choice.